diff --git a/docs/examples/guide/structure.py b/docs/examples/guide/structure.py
index d1766420a..11f285a74 100644
--- a/docs/examples/guide/structure.py
+++ b/docs/examples/guide/structure.py
@@ -7,7 +7,7 @@ from textual.widget import Widget
 class Clock(Widget):
     """A clock app."""
 
-    CSS = """
+    DEFAULT_CSS = """
     Clock {
         content-align: center middle;
     }
diff --git a/docs/examples/light_dark.py b/docs/examples/light_dark.py
index 5e2e9229f..be4351258 100644
--- a/docs/examples/light_dark.py
+++ b/docs/examples/light_dark.py
@@ -4,7 +4,7 @@ from textual.widgets import Button
 
 class ButtonApp(App):
 
-    CSS = """
+    DEFAULT_CSS = """
     Button {
         width: 100%;
     }
diff --git a/old examples/animation.py b/old examples/animation.py
index 0a6efaf19..1fbff9e9d 100644
--- a/old examples/animation.py	
+++ b/old examples/animation.py	
@@ -35,4 +35,4 @@ class SmoothApp(App):
         # self.set_timer(10, lambda: self.action("quit"))
 
 
-SmoothApp.run(log_path="textual.log", log_verbosity=2)
+SmoothApp.run(log_path="textual.log")
diff --git a/sandbox/borders.py b/sandbox/borders.py
index 04161dd62..e67456ffa 100644
--- a/sandbox/borders.py
+++ b/sandbox/borders.py
@@ -8,7 +8,7 @@ from textual.widgets import Placeholder
 
 
 class VerticalContainer(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     VerticalContainer {
         layout: vertical;
         overflow: hidden auto;
@@ -24,7 +24,7 @@ class VerticalContainer(Widget):
 
 
 class Introduction(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     Introduction {
         background: indigo;
         color: white;
diff --git a/sandbox/buttons.py b/sandbox/buttons.py
index 4ffd55dd8..883a457e2 100644
--- a/sandbox/buttons.py
+++ b/sandbox/buttons.py
@@ -23,7 +23,9 @@ class ButtonsApp(App[str]):
 
 
 app = ButtonsApp(
-    log_path="textual.log", css_path="buttons.css", watch_css=True, log_verbosity=2
+    log_path="textual.log",
+    css_path="buttons.css",
+    watch_css=True,
 )
 
 if __name__ == "__main__":
diff --git a/sandbox/color_names.py b/sandbox/color_names.py
index 6e0d904e9..464b65c0c 100644
--- a/sandbox/color_names.py
+++ b/sandbox/color_names.py
@@ -23,7 +23,7 @@ class ColorDisplay(Widget, can_focus=True):
 
 
 class ColorNames(App):
-    CSS = """
+    DEFAULT_CSS = """
     ColorDisplay {
         height: 1;
     }
diff --git a/sandbox/darren/buttons.py b/sandbox/darren/buttons.py
index 4ffd55dd8..883a457e2 100644
--- a/sandbox/darren/buttons.py
+++ b/sandbox/darren/buttons.py
@@ -23,7 +23,9 @@ class ButtonsApp(App[str]):
 
 
 app = ButtonsApp(
-    log_path="textual.log", css_path="buttons.css", watch_css=True, log_verbosity=2
+    log_path="textual.log",
+    css_path="buttons.css",
+    watch_css=True,
 )
 
 if __name__ == "__main__":
diff --git a/sandbox/darren/file_search.py b/sandbox/darren/file_search.py
index a1fbcefb1..240e2bec1 100644
--- a/sandbox/darren/file_search.py
+++ b/sandbox/darren/file_search.py
@@ -62,9 +62,7 @@ class FileSearchApp(App):
         self.file_table.filter = event.value
 
 
-app = FileSearchApp(
-    log_path="textual.log", css_path="file_search.scss", watch_css=True, log_verbosity=2
-)
+app = FileSearchApp(log_path="textual.log", css_path="file_search.scss", watch_css=True)
 
 if __name__ == "__main__":
     result = app.run()
diff --git a/sandbox/fifty.py b/sandbox/fifty.py
index 0a1f91027..c946e47ae 100644
--- a/sandbox/fifty.py
+++ b/sandbox/fifty.py
@@ -5,7 +5,7 @@ from textual.widget import Widget
 
 class FiftyApp(App):
 
-    CSS = """
+    DEFAULT_CSS = """
     Screen {
         layout: vertical;
     }
@@ -24,6 +24,7 @@ class FiftyApp(App):
         yield layout.Horizontal(Widget(), Widget())
         yield layout.Horizontal(Widget(), Widget())
 
+
 app = FiftyApp()
 if __name__ == "__main__":
     app.run()
diff --git a/sandbox/input.py b/sandbox/input.py
index 8df51a03d..5cfba8edc 100644
--- a/sandbox/input.py
+++ b/sandbox/input.py
@@ -61,9 +61,7 @@ class InputApp(App[str]):
             self.celsius.value = f"{celsius:.1f}"
 
 
-app = InputApp(
-    log_path="textual.log", css_path="input.scss", watch_css=True, log_verbosity=2
-)
+app = InputApp(log_path="textual.log", css_path="input.scss", watch_css=True)
 
 if __name__ == "__main__":
     result = app.run()
diff --git a/sandbox/scroll_to_widget.py b/sandbox/scroll_to_widget.py
index 81b0bf83c..209439c16 100644
--- a/sandbox/scroll_to_widget.py
+++ b/sandbox/scroll_to_widget.py
@@ -9,7 +9,7 @@ placeholders_count = 12
 
 
 class VerticalContainer(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     VerticalContainer {
         layout: vertical;
         overflow: hidden auto;
@@ -26,7 +26,7 @@ class VerticalContainer(Widget):
 
 
 class Introduction(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     Introduction {
         background: indigo;
         color: white;
diff --git a/sandbox/vertical_container.py b/sandbox/vertical_container.py
index bb1fca46f..a06e1cd94 100644
--- a/sandbox/vertical_container.py
+++ b/sandbox/vertical_container.py
@@ -10,7 +10,7 @@ initial_placeholders_count = 4
 
 
 class VerticalContainer(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     VerticalContainer {
         layout: vertical;
         overflow: hidden auto;
@@ -30,7 +30,7 @@ class VerticalContainer(Widget):
 
 
 class Introduction(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     Introduction {
         background: indigo;
         color: white;
diff --git a/sandbox/will/add_remove.py b/sandbox/will/add_remove.py
index 5d95bd4da..a34ddd617 100644
--- a/sandbox/will/add_remove.py
+++ b/sandbox/will/add_remove.py
@@ -11,7 +11,7 @@ class Thing(Static):
 
 
 class AddRemoveApp(App):
-    CSS = """
+    DEFAULT_CSS = """
     #buttons {
         dock: top;
         height: auto;       
diff --git a/sandbox/will/calculator.css b/sandbox/will/calculator.css
index 90b1c7617..0d777edfa 100644
--- a/sandbox/will/calculator.css
+++ b/sandbox/will/calculator.css
@@ -9,8 +9,8 @@ Screen {
     table-columns: 1fr;
     table-rows: 2fr 1fr 1fr 1fr 1fr 1fr;
     margin: 1 2;
-    min-height:26;  
-    min-width: 50; 
+    min-height:25;  
+    min-width: 26; 
 }
 
 Button {
@@ -18,18 +18,15 @@ Button {
     height: 100%;    
 }
 
-.display {
+#numbers {
     column-span: 4;
     content-align: right middle;
     padding: 0 1;
     height: 100%;
-    background: $panel-darken-2;
+    background: $primary-lighten-2;
+    color: $text-primary-lighten-2;
 }
 
-.special {
-    tint: $text-panel 20%;
-}
-
-.zero {
+#number-0 {
     column-span: 2;
 }
diff --git a/sandbox/will/calculator.py b/sandbox/will/calculator.py
index 44a6c3926..dabf99376 100644
--- a/sandbox/will/calculator.py
+++ b/sandbox/will/calculator.py
@@ -1,35 +1,143 @@
-from textual.app import App
+from decimal import Decimal
 
+from textual.app import App, ComposeResult
+from textual import events
 from textual.layout import Container
+from textual.reactive import Reactive
 from textual.widgets import Button, Static
 
 
 class CalculatorApp(App):
-    def compose(self):
+    """A working 'desktop' calculator."""
+
+    numbers = Reactive.var("0")
+    show_ac = Reactive.var(True)
+    left = Reactive.var(Decimal("0"))
+    right = Reactive.var(Decimal("0"))
+    value = Reactive.var("")
+    operator = Reactive.var("plus")
+
+    KEY_MAP = {
+        "+": "plus",
+        "-": "minus",
+        ".": "point",
+        "*": "multiply",
+        "/": "divide",
+        "_": "plus-minus",
+        "%": "percent",
+        "=": "equals",
+    }
+
+    def watch_numbers(self, value: str) -> None:
+        """Called when numbers is updated."""
+        # Update the Numbers widget
+        self.query_one("#numbers", Static).update(value)
+
+    def compute_show_ac(self) -> bool:
+        """Compute switch to show AC or C button"""
+        return self.value in ("", "0") and self.numbers == "0"
+
+    def watch_show_ac(self, show_ac: bool) -> None:
+        """Called when show_ac changes."""
+        self.query_one("#c").display = not show_ac
+        self.query_one("#ac").display = show_ac
+
+    def compose(self) -> ComposeResult:
+        """Add our buttons."""
         yield Container(
-            Static("0", classes="display"),
-            Button("AC", classes="special"),
-            Button("+/-", classes="special"),
-            Button("%", classes="special"),
-            Button("÷", variant="warning"),
-            Button("7"),
-            Button("8"),
-            Button("9"),
-            Button("×", variant="warning"),
-            Button("4"),
-            Button("5"),
-            Button("6"),
-            Button("-", variant="warning"),
-            Button("1"),
-            Button("2"),
-            Button("3"),
-            Button("+", variant="warning"),
-            Button("0", classes="operator zero"),
-            Button("."),
-            Button("=", variant="warning"),
+            Static(id="numbers"),
+            Button("AC", id="ac", variant="primary"),
+            Button("C", id="c", variant="primary"),
+            Button("+/-", id="plus-minus", variant="primary"),
+            Button("%", id="percent", variant="primary"),
+            Button("÷", id="divide", variant="warning"),
+            Button("7", id="number-7"),
+            Button("8", id="number-8"),
+            Button("9", id="number-9"),
+            Button("×", id="multiply", variant="warning"),
+            Button("4", id="number-4"),
+            Button("5", id="number-5"),
+            Button("6", id="number-6"),
+            Button("-", id="minus", variant="warning"),
+            Button("1", id="number-1"),
+            Button("2", id="number-2"),
+            Button("3", id="number-3"),
+            Button("+", id="plus", variant="warning"),
+            Button("0", id="number-0"),
+            Button(".", id="point"),
+            Button("=", id="equals", variant="warning"),
             id="calculator",
         )
 
+    def on_key(self, event: events.Key) -> None:
+        """Called when the user presses a key."""
+
+        print(f"KEY {event} was pressed!")
+
+        def press(button_id: str) -> None:
+            self.query_one(f"#{button_id}", Button).press()
+            self.set_focus(None)
+
+        key = event.key
+        if key.isdecimal():
+            press(f"number-{key}")
+        elif key == "c":
+            press("c")
+            press("ac")
+        elif key in self.KEY_MAP:
+            press(self.KEY_MAP[key])
+
+    def on_button_pressed(self, event: Button.Pressed) -> None:
+        """Called when a button is pressed."""
+
+        button_id = event.button.id
+        assert button_id is not None
+
+        self.bell()  # Terminal bell
+
+        def do_math() -> None:
+            """Does the math: LEFT OPERATOR RIGHT"""
+            try:
+                if self.operator == "plus":
+                    self.left += self.right
+                elif self.operator == "minus":
+                    self.left -= self.right
+                elif self.operator == "divide":
+                    self.left /= self.right
+                elif self.operator == "multiply":
+                    self.left *= self.right
+                self.numbers = str(self.left)
+                self.value = ""
+            except Exception:
+                self.numbers = "Error"
+
+        if button_id.startswith("number-"):
+            number = button_id.partition("-")[-1]
+            self.numbers = self.value = self.value.lstrip("0") + number
+        elif button_id == "plus-minus":
+            self.numbers = self.value = str(Decimal(self.value or "0") * -1)
+        elif button_id == "percent":
+            self.numbers = self.value = str(Decimal(self.value or "0") / Decimal(100))
+        elif button_id == "point":
+            if "." not in self.value:
+                self.numbers = self.value = (self.value or "0") + "."
+        elif button_id == "ac":
+            self.value = ""
+            self.left = self.right = Decimal(0)
+            self.operator = "plus"
+            self.numbers = "0"
+        elif button_id == "c":
+            self.value = ""
+            self.numbers = "0"
+        elif button_id in ("plus", "minus", "divide", "multiply"):
+            self.right = Decimal(self.value or "0")
+            do_math()
+            self.operator = button_id
+        elif button_id == "equals":
+            if self.value:
+                self.right = Decimal(self.value)
+            do_math()
+
 
 app = CalculatorApp(css_path="calculator.css")
 if __name__ == "__main__":
diff --git a/sandbox/will/center.py b/sandbox/will/center.py
index b5f5a08b2..dddaf086c 100644
--- a/sandbox/will/center.py
+++ b/sandbox/will/center.py
@@ -3,7 +3,7 @@ from textual.widgets import Static
 
 
 class CenterApp(App):
-    CSS = """
+    DEFAULT_CSS = """
     
     CenterApp Screen {
         layout: center;
diff --git a/sandbox/will/center2.py b/sandbox/will/center2.py
index 1711fd09a..d0191bf48 100644
--- a/sandbox/will/center2.py
+++ b/sandbox/will/center2.py
@@ -4,7 +4,7 @@ from textual.widgets import Static
 
 
 class CenterApp(App):
-    CSS = """
+    DEFAULT_CSS = """
 
     #sidebar {
         dock: left;
@@ -52,4 +52,4 @@ class CenterApp(App):
         )
 
 
-app = CenterApp(log_verbosity=3)
+app = CenterApp()
diff --git a/sandbox/will/just_a_box.py b/sandbox/will/just_a_box.py
index 11c46589f..ea35fa128 100644
--- a/sandbox/will/just_a_box.py
+++ b/sandbox/will/just_a_box.py
@@ -10,7 +10,7 @@ from textual.widget import Widget
 
 
 class Box(Widget, can_focus=True):
-    CSS = "#box {background: blue;}"
+    DEFAULT_CSS = "#box {background: blue;}"
 
     def render(self) -> RenderableType:
         return Panel("Box")
diff --git a/sandbox/will/screens.py b/sandbox/will/screens.py
index c3f655fee..3a9f34dc2 100644
--- a/sandbox/will/screens.py
+++ b/sandbox/will/screens.py
@@ -21,7 +21,7 @@ class NewScreen(Screen):
 
 
 class ScreenApp(App):
-    CSS = """
+    DEFAULT_CSS = """
     ScreenApp Screen {
         background: #111144;
         color: white;
diff --git a/sandbox/will/scroll.py b/sandbox/will/scroll.py
index 57017a6eb..d4b102201 100644
--- a/sandbox/will/scroll.py
+++ b/sandbox/will/scroll.py
@@ -37,9 +37,7 @@ class ButtonsApp(App[str]):
         self.dark = not self.dark
 
 
-app = ButtonsApp(
-    log_path="textual.log", css_path="buttons.css", watch_css=True, log_verbosity=3
-)
+app = ButtonsApp(log_path="textual.log", css_path="buttons.css", watch_css=True)
 
 if __name__ == "__main__":
     result = app.run()
diff --git a/sandbox/will/spacing.css b/sandbox/will/spacing.css
index 911512567..5e1aec208 100644
--- a/sandbox/will/spacing.css
+++ b/sandbox/will/spacing.css
@@ -8,6 +8,6 @@ Static {
     background: blue 20%;
     height: 100%;
     margin: 2 4;
-    min-width: 30;
-    visibility: hidden;
+    min-width: 80;
+    min-height: 40;
 }
diff --git a/sandbox/will/tree.py b/sandbox/will/tree.py
index 158009232..75b1ef283 100644
--- a/sandbox/will/tree.py
+++ b/sandbox/will/tree.py
@@ -5,7 +5,7 @@ from textual.widgets import DirectoryTree
 
 
 class TreeApp(App):
-    CSS = """
+    DEFAULT_CSS = """
     Screen {
         overflow: auto;
 
diff --git a/src/textual/__init__.py b/src/textual/__init__.py
index 197a92f40..7be25a7f4 100644
--- a/src/textual/__init__.py
+++ b/src/textual/__init__.py
@@ -1,18 +1,99 @@
-import inspect
+from __future__ import annotations
 
+import inspect
+from typing import TYPE_CHECKING
+
+import rich.repr
 from rich.console import RenderableType
 
 __all__ = ["log", "panic"]
 
 
-def log(*args: object, verbosity: int = 0, **kwargs) -> None:
-    # TODO: There may be an early-out here for when there is no endpoint for logs
-    from ._context import active_app
+from ._log import LogGroup, LogVerbosity, LogSeverity
 
-    app = active_app.get()
 
-    caller = inspect.stack()[1]
-    app.log(*args, verbosity=verbosity, _textual_calling_frame=caller, **kwargs)
+@rich.repr.auto
+class Logger:
+    """A Textual logger."""
+
+    def __init__(
+        self,
+        group: LogGroup = LogGroup.INFO,
+        verbosity: LogVerbosity = LogVerbosity.NORMAL,
+        severity: LogSeverity = LogSeverity.NORMAL,
+    ) -> None:
+        self._group = group
+        self._verbosity = verbosity
+        self._severity = severity
+
+    def __rich_repr__(self) -> rich.repr.Result:
+        yield self._group, LogGroup.INFO
+        yield self._verbosity, LogVerbosity.NORMAL
+        yield self._severity, LogSeverity.NORMAL
+
+    def __call__(self, *args: object, **kwargs) -> None:
+        from ._context import active_app
+
+        app = active_app.get()
+        caller = inspect.stack()[1]
+        app._log(
+            self._group,
+            self._verbosity,
+            self._severity,
+            *args,
+            _textual_calling_frame=caller,
+            **kwargs,
+        )
+
+    def verbosity(self, verbose: bool) -> Logger:
+        """Get a new logger with selective verbosity.
+
+        Args:
+            verbose (bool): True to use HIGH verbosity, otherwise NORMAL.
+
+        Returns:
+            Logger: New logger.
+        """
+        verbosity = LogVerbosity.HIGH if verbose else LogVerbosity.NORMAL
+        return Logger(self._group, verbosity, LogSeverity.NORMAL)
+
+    @property
+    def verbose(self) -> Logger:
+        """A verbose logger."""
+        return Logger(self._group, LogVerbosity.HIGH)
+
+    @property
+    def critical(self) -> Logger:
+        """A critical logger."""
+        return Logger(self._group, self._verbosity, LogSeverity.CRITICAL)
+
+    @property
+    def event(self) -> Logger:
+        """An event logger."""
+        return Logger(LogGroup.EVENT)
+
+    @property
+    def debug(self) -> Logger:
+        """A debug logger."""
+        return Logger(LogGroup.DEBUG)
+
+    @property
+    def info(self) -> Logger:
+        """An info logger."""
+        return Logger(LogGroup.INFO)
+
+    @property
+    def warning(self) -> Logger:
+        """An info logger."""
+        return Logger(LogGroup.WARNING)
+
+    @property
+    def error(self) -> Logger:
+        """An error logger."""
+        return Logger(LogGroup.ERROR)
+
+
+log = Logger()
 
 
 def panic(*args: RenderableType) -> None:
diff --git a/src/textual/_log.py b/src/textual/_log.py
new file mode 100644
index 000000000..ec9674cda
--- /dev/null
+++ b/src/textual/_log.py
@@ -0,0 +1,27 @@
+from enum import Enum, auto
+
+
+class LogGroup(Enum):
+    """A log group is a classification of the log message (*not* a level)."""
+
+    UNDEFINED = 0  # Mainly for testing
+    EVENT = 1
+    DEBUG = 2
+    INFO = 3
+    WARNING = 4
+    ERROR = 5
+    PRINT = 6
+
+
+class LogVerbosity(Enum):
+    """Tags log messages as being verbose and potentially excluded from output."""
+
+    NORMAL = 0
+    HIGH = 1
+
+
+class LogSeverity(Enum):
+    """Tags log messages as being more severe."""
+
+    NORMAL = 0
+    CRITICAL = 1  # Draws attention to the log message
diff --git a/src/textual/app.py b/src/textual/app.py
index 207d480cb..21c1f479f 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -7,7 +7,7 @@ import os
 import platform
 import sys
 import warnings
-from contextlib import redirect_stdout, redirect_stderr
+from contextlib import redirect_stderr, redirect_stdout
 from datetime import datetime
 from pathlib import PurePath, Path
 from time import perf_counter
@@ -40,7 +40,16 @@ from rich.protocol import is_renderable
 from rich.segment import Segments
 from rich.traceback import Traceback
 
-from . import actions, events, log, messages
+from . import (
+    Logger,
+    LogSeverity,
+    LogGroup,
+    LogVerbosity,
+    actions,
+    events,
+    log,
+    messages,
+)
 from ._animator import Animator
 from ._callback import invoke
 from ._context import active_app
@@ -134,7 +143,6 @@ class App(Generic[ReturnType], DOMNode):
 
     Args:
         driver_class (Type[Driver] | None, optional): Driver class or ``None`` to auto-detect. Defaults to None.
-        log_path (str | PurePath, optional): Path to log file, or "" to disable. Defaults to "".
         log_verbosity (int, optional): Log verbosity from 0-3. Defaults to 1.
         title (str | None, optional): Title of the application. If ``None``, the title is set to the name of the ``App`` subclass. Defaults to ``None``.
         css_path (str | PurePath | None, optional): Path to CSS or ``None`` for no CSS file. Defaults to None.
@@ -142,7 +150,11 @@ class App(Generic[ReturnType], DOMNode):
 
     """
 
-    CSS = """
+    # Inline CSS for quick scripts (generally css_path should be preferred.)
+    CSS = ""
+
+    # Default (lowest priority) CSS
+    DEFAULT_CSS = """
     App {
         background: $background;
         color: $text-background;
@@ -156,11 +168,6 @@ class App(Generic[ReturnType], DOMNode):
     def __init__(
         self,
         driver_class: Type[Driver] | None = None,
-        log_path: str | PurePath = "",
-        log_verbosity: int = 0,
-        log_color_system: Literal[
-            "auto", "standard", "256", "truecolor", "windows"
-        ] = "auto",
         title: str | None = None,
         css_path: str | PurePath | None = None,
         watch_css: bool = False,
@@ -201,20 +208,7 @@ class App(Generic[ReturnType], DOMNode):
         else:
             self._title = title
 
-        self._log_console: Console | None = None
-        self._log_file: TextIO | None = None
-        if log_path:
-            self._log_file = open(log_path, "wt")
-            self._log_console = Console(
-                file=self._log_file,
-                color_system=log_color_system,
-                markup=False,
-                emoji=False,
-                highlight=False,
-                width=100,
-            )
-
-        self.log_verbosity = log_verbosity
+        self._logger = Logger()
 
         self.bindings.bind("ctrl+c", "quit", show=False, allow_forward=False)
         self._refresh_required = False
@@ -486,10 +480,16 @@ class App(Generic[ReturnType], DOMNode):
         """
         return Size(*self.console.size)
 
-    def log(
+    @property
+    def log(self) -> Logger:
+        return self._logger
+
+    def _log(
         self,
+        group: LogGroup,
+        verbosity: LogVerbosity,
+        severity: LogSeverity,
         *objects: Any,
-        verbosity: int = 1,
         _textual_calling_frame: inspect.FrameInfo | None = None,
         **kwargs,
     ) -> None:
@@ -508,22 +508,24 @@ class App(Generic[ReturnType], DOMNode):
         Args:
             verbosity (int, optional): Verbosity level 0-3. Defaults to 1.
         """
-        if verbosity > self.log_verbosity:
-            return
-        if self._log_console is None and not self.devtools.is_connected:
+
+        if not self.devtools.is_connected:
             return
 
-        if self.devtools.is_connected and not _textual_calling_frame:
+        if verbosity.value > LogVerbosity.NORMAL.value and not self.devtools.verbose:
+            return
+
+        if not _textual_calling_frame:
             _textual_calling_frame = inspect.stack()[1]
 
         try:
             if len(objects) == 1 and not kwargs:
-                if self._log_console is not None:
-                    self._log_console.print(objects[0])
-                if self.devtools.is_connected:
-                    self.devtools.log(
-                        DevtoolsLog(objects, caller=_textual_calling_frame)
-                    )
+                self.devtools.log(
+                    DevtoolsLog(objects, caller=_textual_calling_frame),
+                    group,
+                    verbosity,
+                    severity,
+                )
             else:
                 output = " ".join(str(arg) for arg in objects)
                 if kwargs:
@@ -531,12 +533,12 @@ class App(Generic[ReturnType], DOMNode):
                         f"{key}={value!r}" for key, value in kwargs.items()
                     )
                     output = f"{output} {key_values}" if output else key_values
-                if self._log_console is not None:
-                    self._log_console.print(output, soft_wrap=True)
-                if self.devtools.is_connected:
-                    self.devtools.log(
-                        DevtoolsLog(output, caller=_textual_calling_frame)
-                    )
+                self.devtools.log(
+                    DevtoolsLog(output, caller=_textual_calling_frame),
+                    group,
+                    verbosity,
+                    severity,
+                )
         except Exception as error:
             self.on_exception(error)
 
@@ -683,7 +685,6 @@ class App(Generic[ReturnType], DOMNode):
     async def _on_css_change(self) -> None:
         """Called when the CSS changes (if watch_css is True)."""
         if self.css_path is not None:
-
             try:
                 time = perf_counter()
                 stylesheet = self.stylesheet.copy()
@@ -693,8 +694,8 @@ class App(Generic[ReturnType], DOMNode):
                 self.log(f"<stylesheet> loaded {self.css_path!r} in {elapsed:.0f} ms")
             except Exception as error:
                 # TODO: Catch specific exceptions
+                self.log.error(error)
                 self.bell()
-                self.log(error)
             else:
                 self.stylesheet = stylesheet
                 self.reset_styles()
@@ -1042,14 +1043,13 @@ class App(Generic[ReturnType], DOMNode):
         if self.devtools_enabled:
             try:
                 await self.devtools.connect()
-                self.log(f"Connected to devtools ({self.devtools.url})")
+                self.log(f"Connected to devtools ( {self.devtools.url} )")
             except DevtoolsConnectionError:
-                self.log(f"Couldn't connect to devtools ({self.devtools.url})")
+                self.log(f"Couldn't connect to devtools ( {self.devtools.url} )")
 
         self.log("---")
 
         self.log(driver=self.driver_class)
-        self.log(log_verbosity=self.log_verbosity)
         self.log(loop=asyncio.get_running_loop())
         self.log(features=self.features)
 
@@ -1060,13 +1060,23 @@ class App(Generic[ReturnType], DOMNode):
                 self.stylesheet.add_source(
                     css, path=path, is_default_css=True, tie_breaker=tie_breaker
                 )
+            if self.CSS:
+                try:
+                    app_css_path = (
+                        f"{inspect.getfile(self.__class__)}:{self.__class__.__name__}"
+                    )
+                except TypeError:
+                    app_css_path = f"{self.__class__.__name__}"
+                self.stylesheet.add_source(
+                    self.CSS, path=app_css_path, is_default_css=False
+                )
         except Exception as error:
             self.on_exception(error)
             self._print_error_renderables()
             return
 
         if self.css_monitor:
-            self.set_interval(0.5, self.css_monitor, name="css monitor")
+            self.set_interval(0.25, self.css_monitor, name="css monitor")
             self.log("[b green]STARTED[/]", self.css_monitor)
 
         process_messages = super()._process_messages
@@ -1103,7 +1113,7 @@ class App(Generic[ReturnType], DOMNode):
                 if self.is_headless:
                     await run_process_messages()
                 else:
-                    redirector = StdoutRedirector(self.devtools, self._log_file)
+                    redirector = StdoutRedirector(self.devtools)
                     with redirect_stderr(redirector):
                         with redirect_stdout(redirector):  # type: ignore
                             await run_process_messages()
@@ -1116,13 +1126,6 @@ class App(Generic[ReturnType], DOMNode):
             self._print_error_renderables()
             if self.devtools.is_connected:
                 await self._disconnect_devtools()
-                if self._log_console is not None:
-                    self._log_console.print(
-                        f"Disconnected from devtools ({self.devtools.url})"
-                    )
-            if self._log_file is not None:
-                self._log_file.close()
-                self._log_console = None
 
     async def _ready(self) -> None:
         """Called immediately prior to processing messages.
diff --git a/src/textual/cli/cli.py b/src/textual/cli/cli.py
index f91df0e78..3e6cb2359 100644
--- a/src/textual/cli/cli.py
+++ b/src/textual/cli/cli.py
@@ -21,14 +21,16 @@ def run():
 
 
 @run.command(help="Run the Textual Devtools console.")
-def console():
+@click.option("-v", "verbose", help="Enable verbose logs.", is_flag=True)
+@click.option("-x", "--exclude", "exclude", help="Exclude log group(s)", multiple=True)
+def console(verbose: bool, exclude: list[str]) -> None:
     from rich.console import Console
 
     console = Console()
     console.clear()
     console.show_cursor(False)
     try:
-        _run_devtools()
+        _run_devtools(verbose=verbose, exclude=exclude)
     finally:
         console.show_cursor(True)
 
diff --git a/src/textual/css/parse.py b/src/textual/css/parse.py
index 284bd20d8..7ea876355 100644
--- a/src/textual/css/parse.py
+++ b/src/textual/css/parse.py
@@ -347,7 +347,7 @@ def parse(
         path (str): Path to the CSS
         variables (dict[str, str]): Substitution variables to substitute tokens for.
         is_default_rules (bool): True if the rules we're extracting are
-            default (i.e. in Widget.CSS) rules. False if they're from user defined CSS.
+            default (i.e. in Widget.DEFAULT_CSS) rules. False if they're from user defined CSS.
     """
     variable_tokens = tokenize_values(variables or {})
     tokens = iter(substitute_references(tokenize(css, path), variable_tokens))
diff --git a/src/textual/css/styles.py b/src/textual/css/styles.py
index 8dec85133..a476460a9 100644
--- a/src/textual/css/styles.py
+++ b/src/textual/css/styles.py
@@ -571,7 +571,7 @@ class Styles(StylesBase):
         Args:
             specificity (Specificity3): A node specificity.
             is_default_rules (bool): True if the rules we're extracting are
-                default (i.e. in Widget.CSS) rules. False if they're from user defined CSS.
+                default (i.e. in Widget.DEFAULT_CSS) rules. False if they're from user defined CSS.
 
         Returns:
             list[tuple[str, Specificity5, Any]]]: A list containing a tuple of <RULE NAME>, <SPECIFICITY> <RULE VALUE>.
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index 388c44501..d696525a8 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -209,7 +209,7 @@ class Stylesheet:
             css (str): String containing Textual CSS.
             path (str | PurePath): Path to CSS or unique identifier
             is_default_rules (bool): True if the rules we're extracting are
-                default (i.e. in Widget.CSS) rules. False if they're from user defined CSS.
+                default (i.e. in Widget.DEFAULT_CSS) rules. False if they're from user defined CSS.
 
         Raises:
             StylesheetError: If the CSS is invalid.
@@ -555,7 +555,7 @@ if __name__ == "__main__":
     print(app.tree)
     print()
 
-    CSS = """
+    DEFAULT_CSS = """
     App > View {
         layout: dock;
         docks: sidebar=left | widgets=top;
diff --git a/src/textual/devtools/borders.py b/src/textual/devtools/borders.py
index 27813cdfa..376bd79d4 100644
--- a/src/textual/devtools/borders.py
+++ b/src/textual/devtools/borders.py
@@ -14,7 +14,7 @@ Where the fear has gone there will be nothing. Only I will remain."""
 
 
 class BorderButtons(layout.Vertical):
-    CSS = """
+    DEFAULT_CSS = """
     BorderButtons {
         dock: left;
         width: 24;
@@ -34,7 +34,7 @@ class BorderButtons(layout.Vertical):
 class BorderApp(App):
     """Demonstrates the border styles."""
 
-    CSS = """
+    DEFAULT_CSS = """
     Static {
         margin: 2 4;
         padding: 2 4;
diff --git a/src/textual/devtools/client.py b/src/textual/devtools/client.py
index 802bd686a..991f740fd 100644
--- a/src/textual/devtools/client.py
+++ b/src/textual/devtools/client.py
@@ -13,6 +13,8 @@ from typing import Type, Any, NamedTuple
 from rich.console import Console
 from rich.segment import Segment
 
+from .._log import LogGroup, LogVerbosity, LogSeverity
+
 
 class DevtoolsDependenciesMissingError(Exception):
     """Raise when the required devtools dependencies are not installed in the environment"""
@@ -115,6 +117,7 @@ class DevtoolsClient:
         self.websocket: ClientWebSocketResponse | None = None
         self.log_queue: Queue[str | bytes | Type[ClientShutdown]] | None = None
         self.spillover: int = 0
+        self.verbose: bool = False
 
     async def connect(self) -> None:
         """Connect to the devtools server.
@@ -136,7 +139,7 @@ class DevtoolsClient:
         log_queue = self.log_queue
         websocket = self.websocket
 
-        async def update_console():
+        async def update_console() -> None:
             """Coroutine function scheduled as a Task, which listens on
             the websocket for updates from the server regarding any changes
             in the server Console dimensions. When the client learns of this
@@ -150,6 +153,7 @@ class DevtoolsClient:
                         payload = message_json["payload"]
                         self.console.width = payload["width"]
                         self.console.height = payload["height"]
+                        self.verbose = payload.get("verbose", False)
 
         async def send_queued_logs():
             """Coroutine function which is scheduled as a Task, which consumes
@@ -209,7 +213,13 @@ class DevtoolsClient:
             return False
         return not (self.session.closed or self.websocket.closed)
 
-    def log(self, log: DevtoolsLog) -> None:
+    def log(
+        self,
+        log: DevtoolsLog,
+        group: LogGroup = LogGroup.UNDEFINED,
+        verbosity: LogVerbosity = LogVerbosity.NORMAL,
+        severity: LogSeverity = LogSeverity.NORMAL,
+    ) -> None:
         """Queue a log to be sent to the devtools server for display.
 
         Args:
@@ -227,6 +237,9 @@ class DevtoolsClient:
             {
                 "type": "client_log",
                 "payload": {
+                    "group": group.value,
+                    "verbosity": verbosity.value,
+                    "severity": severity.value,
                     "timestamp": int(time()),
                     "path": getattr(log.caller, "filename", ""),
                     "line_number": getattr(log.caller, "lineno", 0),
diff --git a/src/textual/devtools/redirect_output.py b/src/textual/devtools/redirect_output.py
index 801e52c4b..3122da9ec 100644
--- a/src/textual/devtools/redirect_output.py
+++ b/src/textual/devtools/redirect_output.py
@@ -1,12 +1,13 @@
 from __future__ import annotations
 
 import inspect
-from io import TextIOWrapper
+
 from typing import TYPE_CHECKING, cast
-from textual.devtools.client import DevtoolsLog
+from .client import DevtoolsLog
+from .._log import LogGroup, LogVerbosity, LogSeverity
 
 if TYPE_CHECKING:
-    from textual.devtools.client import DevtoolsClient
+    from .devtools.client import DevtoolsClient
 
 
 class StdoutRedirector:
@@ -17,16 +18,13 @@ class StdoutRedirector:
     log file.
     """
 
-    def __init__(
-        self, devtools: DevtoolsClient, log_file: TextIOWrapper | None
-    ) -> None:
+    def __init__(self, devtools: DevtoolsClient) -> None:
         """
         Args:
             devtools (DevtoolsClient): The running Textual app instance.
             log_file (TextIOWrapper): The log file for the Textual App.
         """
         self.devtools = devtools
-        self.log_file = log_file
         self._buffer: list[DevtoolsLog] = []
 
     def write(self, string: str) -> None:
@@ -38,7 +36,7 @@ class StdoutRedirector:
             string (str): The string to write to the buffer.
         """
 
-        if not (self.devtools.is_connected or self.log_file is not None):
+        if not self.devtools.is_connected:
             return
 
         caller = inspect.stack()[1]
@@ -59,7 +57,6 @@ class StdoutRedirector:
         the devtools server and the log file. In the case of the devtools,
         where possible, log messages will be batched and sent as one.
         """
-        self._write_to_log_file()
         self._write_to_devtools()
         self._buffer.clear()
 
@@ -81,20 +78,6 @@ class StdoutRedirector:
         if log_batch:
             self._log_devtools_batched(log_batch)
 
-    def _write_to_log_file(self) -> None:
-        """Write the contents of the buffer to the log file."""
-        if not self.log_file:
-            return
-
-        try:
-            log_text = "".join(str(log.objects_or_string) for log in self._buffer)
-            self.log_file.write(log_text)
-            self.log_file.flush()
-        except OSError:
-            # An error writing to the log file should not be
-            # considered fatal.
-            pass
-
     def _log_devtools_batched(self, log_batch: list[DevtoolsLog]) -> None:
         """Write a single batch of logs to devtools. A batch means contiguous logs
         which have been written from the same line number and file path.
@@ -114,4 +97,9 @@ class StdoutRedirector:
         # that the log message content is a string. The cast below tells mypy this.
         batched_log = "".join(cast(str, log.objects_or_string) for log in log_batch)
         batched_log = batched_log.rstrip()
-        self.devtools.log(DevtoolsLog(batched_log, caller=log_batch[-1].caller))
+        self.devtools.log(
+            DevtoolsLog(batched_log, caller=log_batch[-1].caller),
+            LogGroup.PRINT,
+            LogVerbosity.NORMAL,
+            LogSeverity.NORMAL,
+        )
diff --git a/src/textual/devtools/renderables.py b/src/textual/devtools/renderables.py
index de0c30929..cd0035d47 100644
--- a/src/textual/devtools/renderables.py
+++ b/src/textual/devtools/renderables.py
@@ -18,15 +18,18 @@ from rich.markup import escape
 from rich.rule import Rule
 from rich.segment import Segment, Segments
 from rich.style import Style
+from rich.styled import Styled
 from rich.table import Table
 from rich.text import Text
-
-from textual._border import Border
+from textual._log import LogGroup
 
 DevConsoleMessageLevel = Literal["info", "warning", "error"]
 
 
 class DevConsoleHeader:
+    def __init__(self, verbose: bool = False) -> None:
+        self.verbose = verbose
+
     def __rich_console__(
         self, console: Console, options: ConsoleOptions
     ) -> RenderResult:
@@ -35,6 +38,8 @@ class DevConsoleHeader:
             "[magenta]Run a Textual app with [reverse]textual run --dev my_app.py[/] to connect.\n"
             "[magenta]Press [reverse]Ctrl+C[/] to quit."
         )
+        if self.verbose:
+            preamble.append(Text.from_markup("\n[cyan]Verbose logs enabled"))
         render_options = options.update(width=options.max_width - 4)
         lines = console.render_lines(preamble, render_options)
 
@@ -63,11 +68,17 @@ class DevConsoleLog:
         path: str,
         line_number: int,
         unix_timestamp: int,
+        group: int,
+        verbosity: int,
+        severity: int,
     ) -> None:
         self.segments = segments
         self.path = path
         self.line_number = line_number
         self.unix_timestamp = unix_timestamp
+        self.group = group
+        self.verbosity = verbosity
+        self.severity = severity
 
     def __rich_console__(
         self, console: Console, options: ConsoleOptions
@@ -77,14 +88,26 @@ class DevConsoleLog:
 
         file_link = escape(f"file://{Path(self.path).absolute()}")
         file_and_line = escape(f"{Path(self.path).name}:{self.line_number}")
+        group = LogGroup(self.group).name
+        time = local_time.time()
+        message = Text(
+            f":warning-emoji:  [{time}] {group}"
+            if self.severity > 0
+            else f"[{time}] {group}"
+        )
+        message.stylize("dim")
+
         table.add_row(
-            f"[dim]{local_time.time()}",
+            message,
             Align.right(
                 Text(f"{file_and_line}", style=Style(dim=True, link=file_link))
             ),
         )
         yield table
-        yield Segments(self.segments)
+        if group == "PRINT":
+            yield Styled(Segments(self.segments), "bold")
+        else:
+            yield Segments(self.segments)
 
 
 class DevConsoleNotice:
diff --git a/src/textual/devtools/server.py b/src/textual/devtools/server.py
index a0ad3a149..167696563 100644
--- a/src/textual/devtools/server.py
+++ b/src/textual/devtools/server.py
@@ -36,8 +36,8 @@ async def _on_startup(app: Application) -> None:
     await service.start()
 
 
-def _run_devtools() -> None:
-    app = _make_devtools_aiohttp_app()
+def _run_devtools(verbose: bool, exclude: list[str] | None = None) -> None:
+    app = _make_devtools_aiohttp_app(verbose=verbose, exclude=exclude)
 
     def noop_print(_: str):
         return None
@@ -47,14 +47,17 @@ def _run_devtools() -> None:
 
 def _make_devtools_aiohttp_app(
     size_change_poll_delay_secs: float = DEFAULT_SIZE_CHANGE_POLL_DELAY_SECONDS,
+    verbose: bool = False,
+    exclude: list[str] | None = None,
 ) -> Application:
     app = Application()
 
     app.on_shutdown.append(_on_shutdown)
     app.on_startup.append(_on_startup)
 
+    app["verbose"] = verbose
     app["service"] = DevtoolsService(
-        update_frequency=size_change_poll_delay_secs,
+        update_frequency=size_change_poll_delay_secs, verbose=verbose, exclude=exclude
     )
 
     app.add_routes(
diff --git a/src/textual/devtools/service.py b/src/textual/devtools/service.py
index 5b001d137..7d8ef9a21 100644
--- a/src/textual/devtools/service.py
+++ b/src/textual/devtools/service.py
@@ -16,6 +16,7 @@ from rich.console import Console
 from rich.markup import escape
 import msgpack
 
+from textual._log import LogGroup
 from textual.devtools.renderables import (
     DevConsoleLog,
     DevConsoleNotice,
@@ -30,13 +31,22 @@ class DevtoolsService:
     responsible for tracking connected client applications.
     """
 
-    def __init__(self, update_frequency: float) -> None:
+    def __init__(
+        self,
+        update_frequency: float,
+        verbose: bool = False,
+        exclude: list[str] | None = None,
+    ) -> None:
         """
         Args:
             update_frequency (float): The number of seconds to wait between
                 sending updates of the console size to connected clients.
+            verbose (bool): Enable verbose logging on client.
+            exclude (list[str]): List of log groups to exclude from output.
         """
         self.update_frequency = update_frequency
+        self.verbose = verbose
+        self.exclude = set(name.upper() for name in exclude) if exclude else set()
         self.console = Console()
         self.shutdown_event = asyncio.Event()
         self.clients: list[ClientHandler] = []
@@ -44,7 +54,7 @@ class DevtoolsService:
     async def start(self):
         """Starts devtools tasks"""
         self.size_poll_task = asyncio.create_task(self._console_size_poller())
-        self.console.print(DevConsoleHeader())
+        self.console.print(DevConsoleHeader(verbose=self.verbose))
 
     @property
     def clients_connected(self) -> bool:
@@ -58,6 +68,7 @@ class DevtoolsService:
         """
         current_width = self.console.width
         current_height = self.console.height
+        await self._send_server_info_to_all()
         while not self.shutdown_event.is_set():
             width = self.console.width
             height = self.console.height
@@ -91,6 +102,7 @@ class DevtoolsService:
                 "payload": {
                     "width": self.console.width,
                     "height": self.console.height,
+                    "verbose": self.verbose,
                 },
             }
         )
@@ -168,10 +180,10 @@ class ClientHandler:
 
             type = message["type"]
             if type == "client_log":
-                path = message["payload"]["path"]
-                line_number = message["payload"]["line_number"]
-                timestamp = message["payload"]["timestamp"]
-                encoded_segments = message["payload"]["segments"]
+                payload = message["payload"]
+                if LogGroup(payload.get("group", 0)).name in self.service.exclude:
+                    continue
+                encoded_segments = payload["segments"]
                 segments = pickle.loads(encoded_segments)
                 message_time = time()
                 if (
@@ -183,9 +195,12 @@ class ClientHandler:
                 self.service.console.print(
                     DevConsoleLog(
                         segments=segments,
-                        path=path,
-                        line_number=line_number,
-                        unix_timestamp=timestamp,
+                        path=payload["path"],
+                        line_number=payload["line_number"],
+                        unix_timestamp=payload["timestamp"],
+                        group=payload.get("group", 0),
+                        verbosity=payload.get("verbosity", 0),
+                        severity=payload.get("severity", 0),
                     )
                 )
                 last_message_time = message_time
diff --git a/src/textual/dom.py b/src/textual/dom.py
index a79058e78..ba53f0775 100644
--- a/src/textual/dom.py
+++ b/src/textual/dom.py
@@ -54,8 +54,8 @@ class NoParent(Exception):
 class DOMNode(MessagePump):
     """The base class for object that can be in the Textual DOM (App and Widget)"""
 
-    # Custom CSS
-    CSS: ClassVar[str] = ""
+    # CSS defaults
+    DEFAULT_CSS: ClassVar[str] = ""
 
     # Default classes argument if not supplied
     DEFAULT_CLASSES: str = ""
@@ -198,7 +198,7 @@ class DOMNode(MessagePump):
                 return f"{base.__name__}"
 
         for tie_breaker, base in enumerate(self._node_bases):
-            css = base.CSS.strip()
+            css = base.DEFAULT_CSS.strip()
             if css:
                 css_stack.append((get_path(base), css, -tie_breaker))
 
diff --git a/src/textual/events.py b/src/textual/events.py
index c8bad966e..e868eedab 100644
--- a/src/textual/events.py
+++ b/src/textual/events.py
@@ -19,17 +19,17 @@ if TYPE_CHECKING:
 
 
 @rich.repr.auto
-class Event(Message, verbosity=2):
+class Event(Message):
     def __rich_repr__(self) -> rich.repr.Result:
         return
         yield
 
-    def __init_subclass__(cls, bubble: bool = True, verbosity: int = 1) -> None:
-        super().__init_subclass__(bubble=bubble, verbosity=verbosity)
+    def __init_subclass__(cls, bubble: bool = True, verbose: bool = False) -> None:
+        super().__init_subclass__(bubble=bubble, verbose=verbose)
 
 
 @rich.repr.auto
-class Callback(Event, bubble=False, verbosity=3):
+class Callback(Event, bubble=False, verbose=True):
     def __init__(
         self, sender: MessageTarget, callback: Callable[[], Awaitable[None]]
     ) -> None:
@@ -40,7 +40,7 @@ class Callback(Event, bubble=False, verbosity=3):
         yield "callback", self.callback
 
 
-class InvokeCallbacks(Event, bubble=False):
+class InvokeCallbacks(Event, bubble=False, verbose=True):
     """Sent after the Screen is updated"""
 
 
@@ -83,7 +83,7 @@ class Action(Event):
         yield "action", self.action
 
 
-class Resize(Event, verbosity=2, bubble=False):
+class Resize(Event, bubble=False):
     """Sent when the app or widget has been resized.
     Args:
         sender (MessageTarget): The sender of the event (the Screen).
@@ -116,14 +116,10 @@ class Resize(Event, verbosity=2, bubble=False):
         yield "container_size", self.container_size, self.size
 
 
-class Mount(Event, bubble=False):
+class Mount(Event, bubble=False, verbose=True):
     """Sent when a widget is *mounted* and may receive messages."""
 
 
-class Unmount(Event, bubble=False):
-    """Sent when a widget is unmounted, and may no longer receive messages."""
-
-
 class Remove(Event, bubble=False):
     """Sent to a widget to ask it to remove itself from the DOM."""
 
@@ -217,7 +213,7 @@ class Key(InputEvent):
 
 
 @rich.repr.auto
-class MouseEvent(InputEvent, bubble=True, verbosity=2):
+class MouseEvent(InputEvent, bubble=True):
     """Sent in response to a mouse event.
 
     Args:
@@ -336,21 +332,21 @@ class MouseEvent(InputEvent, bubble=True, verbosity=2):
 
 
 @rich.repr.auto
-class MouseMove(MouseEvent, verbosity=3, bubble=True):
+class MouseMove(MouseEvent, bubble=True, verbose=True):
     """Sent when the mouse cursor moves."""
 
 
 @rich.repr.auto
-class MouseDown(MouseEvent, bubble=True):
+class MouseDown(MouseEvent, bubble=True, verbose=True):
     pass
 
 
 @rich.repr.auto
-class MouseUp(MouseEvent, bubble=True):
+class MouseUp(MouseEvent, bubble=True, verbose=True):
     pass
 
 
-class MouseScrollDown(InputEvent, verbosity=3, bubble=True):
+class MouseScrollDown(InputEvent, bubble=True, verbose=True):
     __slots__ = ["x", "y"]
 
     def __init__(self, sender: MessageTarget, x: int, y: int) -> None:
@@ -359,7 +355,7 @@ class MouseScrollDown(InputEvent, verbosity=3, bubble=True):
         self.y = y
 
 
-class MouseScrollUp(InputEvent, verbosity=3, bubble=True):
+class MouseScrollUp(InputEvent, bubble=True, verbose=True):
     __slots__ = ["x", "y"]
 
     def __init__(self, sender: MessageTarget, x: int, y: int) -> None:
@@ -373,7 +369,7 @@ class Click(MouseEvent, bubble=True):
 
 
 @rich.repr.auto
-class Timer(Event, verbosity=3, bubble=False):
+class Timer(Event, bubble=False, verbose=True):
     __slots__ = ["time", "count", "callback"]
 
     def __init__(
@@ -395,11 +391,11 @@ class Timer(Event, verbosity=3, bubble=False):
         yield "count", self.count
 
 
-class Enter(Event, bubble=False):
+class Enter(Event, bubble=False, verbose=True):
     pass
 
 
-class Leave(Event, bubble=False):
+class Leave(Event, bubble=False, verbose=True):
     pass
 
 
@@ -411,11 +407,11 @@ class Blur(Event, bubble=False):
     pass
 
 
-class DescendantFocus(Event, verbosity=2, bubble=True):
+class DescendantFocus(Event, bubble=True, verbose=True):
     pass
 
 
-class DescendantBlur(Event, verbosity=2, bubble=True):
+class DescendantBlur(Event, bubble=True, verbose=True):
     pass
 
 
diff --git a/src/textual/layout.py b/src/textual/layout.py
index b1cc7a008..b06c347c3 100644
--- a/src/textual/layout.py
+++ b/src/textual/layout.py
@@ -4,7 +4,7 @@ from .widget import Widget
 class Container(Widget):
     """Simple container widget, with vertical layout."""
 
-    CSS = """
+    DEFAULT_CSS = """
     Container {
         layout: vertical;       
         overflow: auto;
@@ -16,13 +16,13 @@ class Vertical(Container):
     """A container widget to align children vertically."""
 
     # Blank CSS is important, otherwise you get a clone of Container
-    CSS = ""
+    DEFAULT_CSS = ""
 
 
 class Horizontal(Container):
     """A container widget to align children horizontally."""
 
-    CSS = """
+    DEFAULT_CSS = """
     Horizontal {
         layout: horizontal;        
     }    
@@ -32,7 +32,7 @@ class Horizontal(Container):
 class Center(Container):
     """A container widget to align children in the center."""
 
-    CSS = """
+    DEFAULT_CSS = """
     Center {
         layout: center;        
     }
diff --git a/src/textual/message.py b/src/textual/message.py
index 869c85ac8..63be90749 100644
--- a/src/textual/message.py
+++ b/src/textual/message.py
@@ -30,7 +30,7 @@ class Message:
 
     sender: MessageTarget
     bubble: ClassVar[bool] = True  # Message will bubble to parent
-    verbosity: ClassVar[int] = 1  # Verbosity (higher the more verbose)
+    verbose: ClassVar[bool] = False  # Message is verbose
     no_dispatch: ClassVar[bool] = False  # Message may not be handled by client code
     namespace: ClassVar[str] = ""  # Namespace to disambiguate messages
 
@@ -52,15 +52,14 @@ class Message:
     def __init_subclass__(
         cls,
         bubble: bool | None = True,
-        verbosity: int | None = 1,
+        verbose: bool = False,
         no_dispatch: bool | None = False,
         namespace: str | None = None,
     ) -> None:
         super().__init_subclass__()
         if bubble is not None:
             cls.bubble = bubble
-        if verbosity is not None:
-            cls.verbosity = verbosity
+        cls.verbose = verbose
         if no_dispatch is not None:
             cls.no_dispatch = no_dispatch
         if namespace is not None:
diff --git a/src/textual/message_pump.py b/src/textual/message_pump.py
index e7eeb4c18..7830ba168 100644
--- a/src/textual/message_pump.py
+++ b/src/textual/message_pump.py
@@ -15,7 +15,7 @@ from functools import partial
 from typing import TYPE_CHECKING, Any, Awaitable, Callable, Iterable
 from weakref import WeakSet
 
-from . import events, log, messages
+from . import events, log, messages, Logger
 from ._callback import invoke
 from ._context import NoActiveAppError, active_app
 from .timer import Timer, TimerCallback
@@ -110,33 +110,9 @@ class MessagePump(metaclass=MessagePumpMeta):
     def is_running(self) -> bool:
         return self._running
 
-    def log(
-        self,
-        *args: Any,
-        verbosity: int = 1,
-        **kwargs,
-    ) -> None:
-        """Write to logs or devtools.
-
-        Positional args will logged. Keyword args will be prefixed with the key.
-
-        Example:
-            ```python
-            data = [1,2,3]
-            self.log("Hello, World", state=data)
-            self.log(self.tree)
-            self.log(locals())
-            ```
-
-        Args:
-            verbosity (int, optional): Verbosity level 0-3. Defaults to 1.
-        """
-        return self.app.log(
-            *args,
-            **kwargs,
-            verbosity=verbosity,
-            _textual_calling_frame=inspect.stack()[1],
-        )
+    @property
+    def log(self) -> Logger:
+        return self.app._logger
 
     def _attach(self, parent: MessagePump) -> None:
         """Set the parent, and therefore attach this node to the tree.
@@ -422,12 +398,11 @@ class MessagePump(metaclass=MessagePumpMeta):
 
         # Look through the MRO to find a handler
         for cls, method in self._get_dispatch_methods(handler_name, message):
-            log(
+            log.event.verbosity(message.verbose)(
                 message,
                 ">>>",
                 self,
                 f"method=<{cls.__name__}.{handler_name}>",
-                verbosity=message.verbosity,
             )
             await invoke(method, message)
 
diff --git a/src/textual/messages.py b/src/textual/messages.py
index 58e4cd2a6..55e42954d 100644
--- a/src/textual/messages.py
+++ b/src/textual/messages.py
@@ -13,7 +13,7 @@ if TYPE_CHECKING:
 
 
 @rich.repr.auto
-class Update(Message, verbosity=3):
+class Update(Message, verbose=True):
     def __init__(self, sender: MessagePump, widget: Widget):
         super().__init__(sender)
         self.widget = widget
@@ -33,13 +33,13 @@ class Update(Message, verbosity=3):
 
 
 @rich.repr.auto
-class Layout(Message, verbosity=3):
+class Layout(Message, verbose=True):
     def can_replace(self, message: Message) -> bool:
         return isinstance(message, Layout)
 
 
 @rich.repr.auto
-class InvokeLater(Message, verbosity=3):
+class InvokeLater(Message, verbose=True):
     def __init__(self, sender: MessagePump, callback: CallbackType) -> None:
         self.callback = callback
         super().__init__(sender)
diff --git a/src/textual/screen.py b/src/textual/screen.py
index 303c76ea0..afeffdc46 100644
--- a/src/textual/screen.py
+++ b/src/textual/screen.py
@@ -29,7 +29,7 @@ UPDATE_PERIOD: Final = 1 / 60
 class Screen(Widget):
     """A widget for the root of the app."""
 
-    CSS = """
+    DEFAULT_CSS = """
     Screen {
         layout: vertical;
         overflow-y: auto;
diff --git a/src/textual/scroll_view.py b/src/textual/scroll_view.py
index 8312be117..6397c9b04 100644
--- a/src/textual/scroll_view.py
+++ b/src/textual/scroll_view.py
@@ -16,7 +16,7 @@ class ScrollView(Widget):
 
     """
 
-    CSS = """
+    DEFAULT_CSS = """
     
     ScrollView {     
         overflow-y: auto;
@@ -87,15 +87,19 @@ class ScrollView(Widget):
             width, height = self.container_size
             if self.show_vertical_scrollbar:
                 self.vertical_scrollbar.window_virtual_size = virtual_size.height
-                self.vertical_scrollbar.window_size = height
+                self.vertical_scrollbar.window_size = (
+                    height - self.scrollbar_size_horizontal
+                )
             if self.show_horizontal_scrollbar:
                 self.horizontal_scrollbar.window_virtual_size = virtual_size.width
-                self.horizontal_scrollbar.window_size = width
+                self.horizontal_scrollbar.window_size = (
+                    width - self.scrollbar_size_vertical
+                )
 
             self.scroll_x = self.validate_scroll_x(self.scroll_x)
             self.scroll_y = self.validate_scroll_y(self.scroll_y)
             self.refresh(layout=False)
-            self.call_later(self.scroll_to, self.scroll_x, self.scroll_y)
+            self.scroll_to(self.scroll_x, self.scroll_y)
 
     def render(self) -> RenderableType:
         """Render the scrollable region (if `render_lines` is not implemented).
diff --git a/src/textual/scrollbar.py b/src/textual/scrollbar.py
index b9dd00774..156954323 100644
--- a/src/textual/scrollbar.py
+++ b/src/textual/scrollbar.py
@@ -22,26 +22,26 @@ class ScrollMessage(Message, bubble=False):
 
 
 @rich.repr.auto
-class ScrollUp(ScrollMessage):
+class ScrollUp(ScrollMessage, verbose=True):
     """Message sent when clicking above handle."""
 
 
 @rich.repr.auto
-class ScrollDown(ScrollMessage):
+class ScrollDown(ScrollMessage, verbose=True):
     """Message sent when clicking below handle."""
 
 
 @rich.repr.auto
-class ScrollLeft(ScrollMessage):
+class ScrollLeft(ScrollMessage, verbose=True):
     """Message sent when clicking above handle."""
 
 
 @rich.repr.auto
-class ScrollRight(ScrollMessage):
+class ScrollRight(ScrollMessage, verbose=True):
     """Message sent when clicking below handle."""
 
 
-class ScrollTo(ScrollMessage):
+class ScrollTo(ScrollMessage, verbose=True):
     """Message sent when click and dragging handle."""
 
     def __init__(
@@ -93,9 +93,9 @@ class ScrollBarRender:
     ) -> Segments:
 
         if vertical:
-            bars = [" ", "▁", "▂", "▃", "▄", "▅", "▆", "▇", "█"]
+            bars = ["▁", "▂", "▃", "▄", "▅", "▆", "▇", " "]
         else:
-            bars = ["█", "▉", "▊", "▋", "▌", "▍", "▎", "▏", " "]
+            bars = ["▉", "▊", "▋", "▌", "▍", "▎", "▏", " "]
 
         back = back_color
         bar = bar_color
@@ -110,11 +110,11 @@ class ScrollBarRender:
         if window_size and size and virtual_size and size != virtual_size:
             step_size = virtual_size / size
 
-            start = int(position / step_size * 9)
-            end = start + max(9, int(ceil(window_size / step_size * 9)))
+            start = int(position / step_size * 8)
+            end = start + max(8, int(ceil(window_size / step_size * 8)))
 
-            start_index, start_bar = divmod(start, 9)
-            end_index, end_bar = divmod(end, 9)
+            start_index, start_bar = divmod(start, 8)
+            end_index, end_bar = divmod(end, 8)
 
             upper = {"@click": "scroll_up"}
             lower = {"@click": "scroll_down"}
@@ -130,19 +130,23 @@ class ScrollBarRender:
             ] * (end_index - start_index)
 
             if start_index < len(segments):
-                segments[start_index] = _Segment(
-                    bars[8 - start_bar] * width_thickness,
-                    _Style(bgcolor=back, color=bar, meta=foreground_meta)
-                    if vertical
-                    else _Style(bgcolor=bar, color=back, meta=foreground_meta),
-                )
+                bar_character = bars[7 - start_bar]
+                if bar_character != " ":
+                    segments[start_index] = _Segment(
+                        bar_character * width_thickness,
+                        _Style(bgcolor=back, color=bar, meta=foreground_meta)
+                        if vertical
+                        else _Style(bgcolor=bar, color=back, meta=foreground_meta),
+                    )
             if end_index < len(segments):
-                segments[end_index] = _Segment(
-                    bars[8 - end_bar] * width_thickness,
-                    _Style(bgcolor=bar, color=back, meta=foreground_meta)
-                    if vertical
-                    else _Style(bgcolor=back, color=bar, meta=foreground_meta),
-                )
+                bar_character = bars[7 - end_bar]
+                if bar_character != " ":
+                    segments[end_index] = _Segment(
+                        bar_character * width_thickness,
+                        _Style(bgcolor=bar, color=back, meta=foreground_meta)
+                        if vertical
+                        else _Style(bgcolor=back, color=bar, meta=foreground_meta),
+                    )
         else:
             style = _Style(bgcolor=back)
             segments = [_Segment(blank, style=style)] * int(size)
diff --git a/src/textual/widget.py b/src/textual/widget.py
index 3f0e2f2bb..2555a8584 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -72,7 +72,7 @@ class Widget(DOMNode):
 
     """
 
-    CSS = """
+    DEFAULT_CSS = """
     Widget{
         scrollbar-background: $panel-darken-1;
         scrollbar-background-hover: $panel-darken-2;
@@ -1248,16 +1248,19 @@ class Widget(DOMNode):
                 width, height = self.container_size
                 if self.show_vertical_scrollbar:
                     self.vertical_scrollbar.window_virtual_size = virtual_size.height
-                    self.vertical_scrollbar.window_size = height
+                    self.vertical_scrollbar.window_size = (
+                        height - self.scrollbar_size_horizontal
+                    )
                 if self.show_horizontal_scrollbar:
                     self.horizontal_scrollbar.window_virtual_size = virtual_size.width
-                    self.horizontal_scrollbar.window_size = width
+                    self.horizontal_scrollbar.window_size = (
+                        width - self.scrollbar_size_vertical
+                    )
 
                 self.scroll_x = self.validate_scroll_x(self.scroll_x)
                 self.scroll_y = self.validate_scroll_y(self.scroll_y)
                 self.refresh(layout=True)
                 self.scroll_to(self.scroll_x, self.scroll_y)
-                # self.call_later(self.scroll_to, self.scroll_x, self.scroll_y)
             else:
                 self.refresh()
 
@@ -1396,7 +1399,7 @@ class Widget(DOMNode):
         if not self.check_message_enabled(message):
             return True
         if not self.is_running:
-            self.log(self, f"IS NOT RUNNING, {message!r} not sent")
+            self.log.warning(self, f"IS NOT RUNNING, {message!r} not sent")
         return await super().post_message(message)
 
     async def _on_idle(self, event: events.Idle) -> None:
diff --git a/src/textual/widgets/_button.py b/src/textual/widgets/_button.py
index 3121ef9c4..68c50839a 100644
--- a/src/textual/widgets/_button.py
+++ b/src/textual/widgets/_button.py
@@ -29,7 +29,7 @@ class InvalidButtonVariant(Exception):
 class Button(Widget, can_focus=True):
     """A simple clickable button."""
 
-    CSS = """
+    DEFAULT_CSS = """
     Button {
         width: auto;
         min-width: 10;
diff --git a/src/textual/widgets/_data_table.py b/src/textual/widgets/_data_table.py
index c4059c000..71a667c08 100644
--- a/src/textual/widgets/_data_table.py
+++ b/src/textual/widgets/_data_table.py
@@ -106,7 +106,7 @@ class Coord(NamedTuple):
 
 class DataTable(ScrollView, Generic[CellType], can_focus=True):
 
-    CSS = """
+    DEFAULT_CSS = """
     DataTable {
         background: $surface;
         color: $text-surface;       
diff --git a/src/textual/widgets/_footer.py b/src/textual/widgets/_footer.py
index 66211a450..987193087 100644
--- a/src/textual/widgets/_footer.py
+++ b/src/textual/widgets/_footer.py
@@ -13,7 +13,7 @@ from ..widget import Widget
 @rich.repr.auto
 class Footer(Widget):
 
-    CSS = """
+    DEFAULT_CSS = """
     Footer {
         background: $accent;
         color: $text-accent;
diff --git a/src/textual/widgets/_header.py b/src/textual/widgets/_header.py
index e54c6ce6d..26cb4bea0 100644
--- a/src/textual/widgets/_header.py
+++ b/src/textual/widgets/_header.py
@@ -11,7 +11,7 @@ from ..reactive import Reactive, watch
 class HeaderIcon(Widget):
     """Display an 'icon' on the left of the header."""
 
-    CSS = """
+    DEFAULT_CSS = """
     HeaderIcon {
         dock: left;
         padding: 0 1;
@@ -28,7 +28,7 @@ class HeaderIcon(Widget):
 class HeaderClock(Widget):
     """Display a clock on the right of the header."""
 
-    CSS = """
+    DEFAULT_CSS = """
     HeaderClock {
         dock: right;
         width: auto;
@@ -50,7 +50,7 @@ class HeaderClock(Widget):
 class HeaderTitle(Widget):
     """Display the title / subtitle in the header."""
 
-    CSS = """
+    DEFAULT_CSS = """
     HeaderTitle {
         content-align: center middle;
         width: 100%;
@@ -70,7 +70,7 @@ class HeaderTitle(Widget):
 class Header(Widget):
     """A header widget with icon and clock."""
 
-    CSS = """
+    DEFAULT_CSS = """
     Header {
         dock: top;
         width: 100%;
diff --git a/src/textual/widgets/_pretty.py b/src/textual/widgets/_pretty.py
index 3d4369e52..ff43350f5 100644
--- a/src/textual/widgets/_pretty.py
+++ b/src/textual/widgets/_pretty.py
@@ -7,7 +7,7 @@ from ..widget import Widget
 
 
 class Pretty(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     Static {
         height: auto;
     }
diff --git a/src/textual/widgets/_static.py b/src/textual/widgets/_static.py
index 1813d530f..824248ce7 100644
--- a/src/textual/widgets/_static.py
+++ b/src/textual/widgets/_static.py
@@ -25,7 +25,7 @@ def _check_renderable(renderable: object):
 
 
 class Static(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     Static {
         height: auto;
     }
diff --git a/src/textual/widgets/_tree_control.py b/src/textual/widgets/_tree_control.py
index 86d2b0e9e..b3200c071 100644
--- a/src/textual/widgets/_tree_control.py
+++ b/src/textual/widgets/_tree_control.py
@@ -169,7 +169,7 @@ class TreeClick(Generic[NodeDataType], Message, bubble=True):
 
 
 class TreeControl(Generic[NodeDataType], Widget, can_focus=True):
-    CSS = """
+    DEFAULT_CSS = """
     TreeControl {
         background: $panel;
         color: $text-panel;
diff --git a/src/textual/widgets/text_input.py b/src/textual/widgets/text_input.py
index 4e9c71f62..966faf2a1 100644
--- a/src/textual/widgets/text_input.py
+++ b/src/textual/widgets/text_input.py
@@ -112,7 +112,7 @@ class TextInput(TextWidgetBase, can_focus=True):
             suggestion will be displayed as dim text similar to suggestion text in the zsh or fish shells.
     """
 
-    CSS = """
+    DEFAULT_CSS = """
     TextInput {
         width: auto;
         background: $surface;
@@ -417,7 +417,7 @@ class TextInput(TextWidgetBase, can_focus=True):
 
 
 class TextArea(Widget):
-    CSS = """
+    DEFAULT_CSS = """
     TextArea { overflow: auto auto; height: 5; background: $primary-darken-1; }
 """
 
@@ -428,7 +428,7 @@ class TextArea(Widget):
 class TextAreaChild(TextWidgetBase, can_focus=True):
     # TODO: Not nearly ready for prime-time, but it exists to help
     #  model the superclass.
-    CSS = "TextAreaChild { height: auto; background: $primary-darken-1; }"
+    DEFAULT_CSS = "TextAreaChild { height: auto; background: $primary-darken-1; }"
     STOP_PROPAGATE = {"tab", "shift+tab"}
 
     def render(self) -> RenderableType:
diff --git a/tests/css/test_stylesheet.py b/tests/css/test_stylesheet.py
index ac732f6f7..be54fe936 100644
--- a/tests/css/test_stylesheet.py
+++ b/tests/css/test_stylesheet.py
@@ -106,16 +106,18 @@ def test_stylesheet_apply_user_css_over_widget_css():
     user_css = ".a {color: red; tint: yellow;}"
 
     class MyWidget(Widget):
-        CSS = ".a {color: blue !important; background: lime;}"
+        DEFAULT_CSS = ".a {color: blue !important; background: lime;}"
 
     node = MyWidget()
     node.add_class("a")
 
     stylesheet = _make_user_stylesheet(user_css)
-    stylesheet.add_source(MyWidget.CSS, "widget.py:MyWidget", is_default_css=True)
+    stylesheet.add_source(
+        MyWidget.DEFAULT_CSS, "widget.py:MyWidget", is_default_css=True
+    )
     stylesheet.apply(node)
 
-    # The node is red because user CSS overrides Widget.CSS
+    # The node is red because user CSS overrides Widget.DEFAULT_CSS
     assert node.styles.color == Color(255, 0, 0)
     # The background colour defined in the Widget still applies, since user CSS doesn't override it
     assert node.styles.background == Color(0, 255, 0)
diff --git a/tests/devtools/conftest.py b/tests/devtools/conftest.py
index 92f6253a3..b819512e2 100644
--- a/tests/devtools/conftest.py
+++ b/tests/devtools/conftest.py
@@ -27,8 +27,3 @@ async def devtools(aiohttp_client, server):
     yield devtools
     await devtools.disconnect()
     await client.close()
-
-
-@pytest.fixture
-def in_memory_logfile():
-    yield StringIO()
diff --git a/tests/devtools/test_devtools.py b/tests/devtools/test_devtools.py
index f66766445..b8c65bfd1 100644
--- a/tests/devtools/test_devtools.py
+++ b/tests/devtools/test_devtools.py
@@ -37,6 +37,9 @@ def test_log_message_render(console):
         path="abc/hello.py",
         line_number=123,
         unix_timestamp=TIMESTAMP,
+        group=0,
+        verbosity=0,
+        severity=0,
     )
     table = next(iter(message.__rich_console__(console, console.options)))
 
@@ -52,7 +55,7 @@ def test_log_message_render(console):
     local_time = datetime.fromtimestamp(TIMESTAMP)
     string_timestamp = local_time.time()
 
-    assert left == f"[dim]{string_timestamp}"
+    assert left.plain == f"[{string_timestamp}] UNDEFINED"
     assert right.align == "right"
     assert "hello.py:123" in right.renderable
 
diff --git a/tests/devtools/test_devtools_client.py b/tests/devtools/test_devtools_client.py
index 84a57b3c6..0f5f6e490 100644
--- a/tests/devtools/test_devtools_client.py
+++ b/tests/devtools/test_devtools_client.py
@@ -36,15 +36,20 @@ async def test_devtools_log_places_encodes_and_queues_message(devtools):
     queued_log = await devtools.log_queue.get()
     queued_log_data = msgpack.unpackb(queued_log)
     print(repr(queued_log_data))
-    assert queued_log_data == {
-        "type": "client_log",
-        "payload": {
-            "timestamp": 1649166819,
-            "path": "a/b/c.py",
-            "line_number": 123,
-            "segments": b"\x80\x04\x95B\x00\x00\x00\x00\x00\x00\x00]\x94(\x8c\x0crich.segment\x94\x8c\x07Segment\x94\x93\x94\x8c\rHello, world!\x94NN\x87\x94\x81\x94h\x03\x8c\x01\n\x94NN\x87\x94\x81\x94e.",
-        },
-    }
+
+
+{
+    "type": "client_log",
+    "payload": {
+        "group": 0,
+        "verbosity": 0,
+        "severity": 0,
+        "timestamp": 1649166819,
+        "path": "a/b/c.py",
+        "line_number": 123,
+        "segments": b"\x80\x04\x95@\x00\x00\x00\x00\x00\x00\x00]\x94(\x8c\x0crich.segment\x94\x8c\x07Segment\x94\x93\x94\x8c\x0bhello world\x94NN\x87\x94\x81\x94h\x03\x8c\x01\n\x94NN\x87\x94\x81\x94e.",
+    },
+}
 
 
 @time_machine.travel(datetime.utcfromtimestamp(TIMESTAMP))
@@ -57,6 +62,9 @@ async def test_devtools_log_places_encodes_and_queues_many_logs_as_string(devtoo
     assert queued_log_data == {
         "type": "client_log",
         "payload": {
+            "group": 0,
+            "verbosity": 0,
+            "severity": 0,
             "timestamp": 1649166819,
             "path": "a/b/c.py",
             "line_number": 123,
diff --git a/tests/devtools/test_redirect_output.py b/tests/devtools/test_redirect_output.py
index 349c2aa69..fd4659940 100644
--- a/tests/devtools/test_redirect_output.py
+++ b/tests/devtools/test_redirect_output.py
@@ -14,7 +14,7 @@ TIMESTAMP = 1649166819
 async def test_print_redirect_to_devtools_only(devtools):
     await devtools._stop_log_queue_processing()
 
-    with redirect_stdout(StdoutRedirector(devtools, None)):  # type: ignore
+    with redirect_stdout(StdoutRedirector(devtools)):  # type: ignore
         print("Hello, world!")
 
     assert devtools.log_queue.qsize() == 1
@@ -32,28 +32,26 @@ async def test_print_redirect_to_devtools_only(devtools):
     )
 
 
-async def test_print_redirect_to_logfile_only(devtools, in_memory_logfile):
+async def test_print_redirect_to_logfile_only(devtools):
     await devtools.disconnect()
-    with redirect_stdout(StdoutRedirector(devtools, in_memory_logfile)):  # type: ignore
+    with redirect_stdout(StdoutRedirector(devtools)):  # type: ignore
         print("Hello, world!")
-    assert in_memory_logfile.getvalue() == "Hello, world!\n"
 
 
-async def test_print_redirect_to_devtools_and_logfile(devtools, in_memory_logfile):
+async def test_print_redirect_to_devtools_and_logfile(devtools):
     await devtools._stop_log_queue_processing()
 
-    with redirect_stdout(StdoutRedirector(devtools, in_memory_logfile)):  # type: ignore
+    with redirect_stdout(StdoutRedirector(devtools)):  # type: ignore
         print("Hello, world!")
 
     assert devtools.log_queue.qsize() == 1
-    assert in_memory_logfile.getvalue() == "Hello, world!\n"
 
 
 @time_machine.travel(datetime.fromtimestamp(TIMESTAMP))
-async def test_print_without_flush_not_sent_to_devtools(devtools, in_memory_logfile):
+async def test_print_without_flush_not_sent_to_devtools(devtools):
     await devtools._stop_log_queue_processing()
 
-    with redirect_stdout(StdoutRedirector(devtools, in_memory_logfile)):  # type: ignore
+    with redirect_stdout(StdoutRedirector(devtools)):  # type: ignore
         # End is no longer newline character, so print will no longer
         # flush the output buffer by default.
         print("Hello, world!", end="")
@@ -62,44 +60,19 @@ async def test_print_without_flush_not_sent_to_devtools(devtools, in_memory_logf
 
 
 @time_machine.travel(datetime.fromtimestamp(TIMESTAMP))
-async def test_print_forced_flush_sent_to_devtools(devtools, in_memory_logfile):
+async def test_print_forced_flush_sent_to_devtools(devtools):
     await devtools._stop_log_queue_processing()
 
-    with redirect_stdout(StdoutRedirector(devtools, in_memory_logfile)):  # type: ignore
+    with redirect_stdout(StdoutRedirector(devtools)):  # type: ignore
         print("Hello, world!", end="", flush=True)
 
     assert devtools.log_queue.qsize() == 1
 
 
 @time_machine.travel(datetime.fromtimestamp(TIMESTAMP))
-async def test_print_multiple_args_batched_as_one_log(devtools, in_memory_logfile):
+async def test_print_multiple_args_batched_as_one_log(devtools):
     await devtools._stop_log_queue_processing()
-
-    with redirect_stdout(StdoutRedirector(devtools, in_memory_logfile)):  # type: ignore
-        # We call print with multiple arguments here, but it
-        # results in a single log added to the log queue.
-        print("Hello", "world", "multiple")
-
-    assert devtools.log_queue.qsize() == 1
-
-    queued_log = await devtools.log_queue.get()
-    queued_log_json = json.loads(queued_log)
-    payload = queued_log_json["payload"]
-
-    assert queued_log_json["type"] == "client_log"
-    assert payload["timestamp"] == TIMESTAMP
-    assert (
-        payload["encoded_segments"]
-        == "gANdcQAoY3JpY2guc2VnbWVudApTZWdtZW50CnEBWBQAAABIZWxsbyB3b3JsZCBtdWx0aXBsZXECTk6HcQOBcQRoAVgBAAAACnEFTk6HcQaBcQdlLg=="
-    )
-    assert len(payload["path"]) > 0
-    assert payload["line_number"] != 0
-
-
-@time_machine.travel(datetime.fromtimestamp(TIMESTAMP))
-async def test_print_multiple_args_batched_as_one_log(devtools, in_memory_logfile):
-    await devtools._stop_log_queue_processing()
-    redirector = StdoutRedirector(devtools, in_memory_logfile)
+    redirector = StdoutRedirector(devtools)
     with redirect_stdout(redirector):  # type: ignore
         # This print adds 3 messages to the buffer that can be batched
         print("The first", "batch", "of logs", end="")
@@ -111,10 +84,10 @@ async def test_print_multiple_args_batched_as_one_log(devtools, in_memory_logfil
 
 
 @time_machine.travel(datetime.fromtimestamp(TIMESTAMP))
-async def test_print_strings_containing_newline_flushed(devtools, in_memory_logfile):
+async def test_print_strings_containing_newline_flushed(devtools):
     await devtools._stop_log_queue_processing()
 
-    with redirect_stdout(StdoutRedirector(devtools, in_memory_logfile)):  # type: ignore
+    with redirect_stdout(StdoutRedirector(devtools)):  # type: ignore
         # Flushing is disabled since end="", but the first
         # string will be flushed since it contains a newline
         print("Hel\nlo", end="")
@@ -124,10 +97,10 @@ async def test_print_strings_containing_newline_flushed(devtools, in_memory_logf
 
 
 @time_machine.travel(datetime.fromtimestamp(TIMESTAMP))
-async def test_flush_flushes_buffered_logs(devtools, in_memory_logfile):
+async def test_flush_flushes_buffered_logs(devtools):
     await devtools._stop_log_queue_processing()
 
-    redirector = StdoutRedirector(devtools, in_memory_logfile)
+    redirector = StdoutRedirector(devtools)
     with redirect_stdout(redirector):  # type: ignore
         print("x", end="")
 
diff --git a/tests/test_integration_layout.py b/tests/test_integration_layout.py
index d60112393..46106dd5f 100644
--- a/tests/test_integration_layout.py
+++ b/tests/test_integration_layout.py
@@ -110,7 +110,7 @@ async def test_composition_of_vertical_container_with_children(
     expected_placeholders_offset_x: int,
 ):
     class VerticalContainer(Widget):
-        CSS = (
+        DEFAULT_CSS = (
             """
         VerticalContainer {
             layout: vertical;
@@ -304,7 +304,7 @@ async def test_scrollbar_size_impact_on_the_layout(
     class LargeWidgetContainer(Widget):
         # TODO: Once textual#581 ("Default versus User CSS") is solved the following CSS should just use the
         #  "LargeWidgetContainer" selector, without having to use a more specific one to be able to override Widget's CSS:
-        CSS = """
+        DEFAULT_CSS = """
         #large-widget-container {
             width: 20;
             height: 20;
diff --git a/tests/test_integration_scrolling.py b/tests/test_integration_scrolling.py
index b3059b146..8c4175c62 100644
--- a/tests/test_integration_scrolling.py
+++ b/tests/test_integration_scrolling.py
@@ -48,7 +48,7 @@ async def test_scroll_to_widget(
     last_screen_expected_placeholder_ids: Sequence[int],
 ):
     class VerticalContainer(Widget):
-        CSS = """
+        DEFAULT_CSS = """
         VerticalContainer {
             layout: vertical;
             overflow: hidden auto;
@@ -60,7 +60,7 @@ async def test_scroll_to_widget(
         """
 
     class MyTestApp(AppTest):
-        CSS = """
+        DEFAULT_CSS = """
         Placeholder {
             height: 5; /* minimal height to see the name of a Placeholder */
         }
diff --git a/tests/utilities/test_app.py b/tests/utilities/test_app.py
index e23952b23..64eb637cb 100644
--- a/tests/utilities/test_app.py
+++ b/tests/utilities/test_app.py
@@ -25,20 +25,11 @@ from textual.geometry import Size, Region
 
 
 class AppTest(App):
-    def __init__(
-        self,
-        *,
-        test_name: str,
-        size: Size,
-        log_verbosity: int = 2,
-    ):
+    def __init__(self, *, test_name: str, size: Size):
         # Tests will log in "/tests/test.[test name].log":
         log_path = Path(__file__).parent.parent / f"test.{test_name}.log"
         super().__init__(
             driver_class=DriverTest,
-            log_path=log_path,
-            log_verbosity=log_verbosity,
-            log_color_system="256",
         )
 
         # Let's disable all features by default