It was on D (as in uppercase D, or shift-d), but I feel this was going to be
confusing given that there is still this slight mixup with the display of
letters in the footer, and what was bound, etc.
So... make it obvious what to press.
Remember, 'd' can't be used because it's a movement key in this game.
See https://github.com/Textualize/textual/pull/963#discussion_r1000546514
Personally I prefer the approach I was using in that it's one less bit of
hard-coded metadata. On the other hand I can appreciate that reducing the
number of possibly-confusing things in an example plays better with people
who may be both new to Textual *and* to Python.
Because Textual uses on_ for event handlers there was the danger of a name
clash; so to keep things as clear as possible this renames anything to do
with "on" (method names, properties, style classes) so that it talks about
"filled" instead.
See https://github.com/Textualize/textual/pull/963#discussion_r1000544563
It had been suggested to me that these would be needed, but in testing here
I'm not seeing that. So, until I find out otherwise, let's simplify things
and drop that.
Originally I was doing everything in the DOM, using just the primitive
widgets. Given that I recently created an actual GameCell widget (which
simply inherits from a Button, but still...) it makes sense to now have
row/col properties as part of that.
