* Player character now experiences acceleration and friction when
walking around the map!
* Actor position and movement had to be converted from int's
(render.Point) to float64's to support fine-grained acceleration
steps.
* Added "physics" package and physics.Vector to be a float64 counterpart
for render.Point. Vector is used for uix.Actor.Position() for the sake
of movement math. Vector is flattened back to a render.Point for
collision purposes, since the levels and hitboxes are pixel-bound.
* Refactor the uix.Actor to no longer extend the doodads.Drawing (so it
can have a Position that's a Vector instead of a Point). This broke
some code that expected `.Doodad` to directly reference the
Drawing.Doodad: now you had to refer to it as `a.Drawing.Doodad` which
was ugly. Added convenience method .Doodad() for a shortcut.
* Moved functions like GetBoundingRect() from doodads package to
collision, where it uses its own slimmer Actor interface for just the
relevant methods it needs.
* Implement the handler code for `return false` when actors are
colliding with each other and wish to act like solid walls.
* The locked doors will `return false` when they're closed and the
colliding actor does not have the matching key.
* Add arbitrary key/value storage to Actors. The colored keys will set
an actor value "key:%TITLE%" on the one who touched the key before
destroying itself. The colored doors check that key when touched to
decide whether to open.
* The trapdoor now only opens if you're touching it from the top (your
overlap box Y value is 0), but if you touch it from below and the door
is closed, it acts like a solid object.
* Events.OnCollide now receives a CollideEvent object, which makes
available the .Actor who collided and the .Overlap rect which is
zero-relative to the target actor. Doodad scripts can use the .Overlap
to see WHERE in their own box the other actor has intruded.
* Update the LockedDoor and ElectricDoor doodads to detect when the
player has entered their inner rect (since their doors are narrower
than their doodad size)
* Update the Button doodads to only press in when the player actually
touches them (because their sizes are shorter than their doodad
height)
* Update the Trapdoor to only trigger its animation when the board
along its top has been touched, not when the empty space below was
touched from the bottom.
* Events.OnLeave now implemented and fires when an actor who was
previously intersecting your doodad has left.
* The engine detects when an event JS callback returns false.
Eventually, the OnCollide can return false to signify the collision is
not accepted and the actor should be bumped away as if they hit solid
geometry.
* Add animation support for Doodad actors (Play Mode) into the core
engine, so that the Doodad script can register named animations and
play them without managing all the details themselves.
* Doodad API functions on Self: AddAnimation, PlayAnimation,
StopAnimation, IsAnimating
* CLI: the `doodad convert` command will name each layer after the
filename used as the input image.
* CLI: fix the `doodad convert` command creating duplicate Palette
colors when converting a series of input images into a Doodad.
* CLI: fix the `doodad convert` command to share the same Palette when
converting each frame (layer) of a doodad so subsequent layers find
the correct color swatches for serialization.
* Scripting: add timers and intervals to Doodad scripts to allow them to
animate themselves or add delayed callbacks. The timers have the same
API as a web browser: setTimeout(), setInterval(), clearTimeout(),
clearInterval().
* Add support for uix.Actor to change its currently rendered layer in
the level. For example a Button Doodad can set its image to Layer 1
(pressed) when touched by the player, and Trapdoors can cycle through
their layers to animate opening and closing.
* Usage from a Doodad script: Self.ShowLayer(1)
* Default Doodads: added scripts for all Buttons, Doors, Keys and the
Trapdoor to run their various animations when touched (in the case of
Keys, destroy themselves when touched, because there is no player
inventory yet)
