Add ability to hide/show the mouse cursor.
Add basic game state handling.

States for starting, running, respawning after losing a ball, game
over, and winning. The game is basically playable now, with absolutely
no frills.
Reorganize code (no actual changes)
Rename alignment: to align: for consistency.

All other functions use align: rather than alignment:, so make
<text-field> do the same in its init arg.
Fix rendering for <root-visual>

Refactor to ensure <root-visual> performs all the same actions on
rendering as any child of a <group-visual>. In particular this means
support for alpha and pre-/post-render events.
Make sure render-color is applied where expected.
Don't send mouse events to invisible <visual>s
Fix bug in \- on <rect>
Add align: keyword to <image> creation functions.

This is just a convenience to set the anchor-pt for common cases,
without needing to compute it manually (e.g., when we want the anchor
point to be the center of the image).
Polish the bricks example app.

Lots of changes, including sounds, effects, improved visuals (including
a couple of images), game flow (multiple lives, game states (respawn,
win, game over, etc)). Plus numerous tweaks and fixes.
Formatting: Condense key codes in library file.

They were just taking up too much vertical space.
Add with-disposable macro.

Macro to safely declare and use one or more disposable objects within a
scope and ensure they are disposed on exit from the scope.
Using with-disposable macro, plus formatting.