* 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.
* The `doodad edit-doodad` command now allows setting custom key/value
tags in doodad files, for extra data storage useful to their scripts.
* Colored keys and doors now store a `color` tag with the appropriate
color so that their scripts don't have to parse their Title to find
that information.
* Trapdoors now store a `direction` tag to hold the direction the door
is facing.
* Improve the collision detection algorithm so that Actor OnCollide
scripts get called more often WHILE an actor is moving, to prevent a
fast-moving actor from zipping right through the "solid" hitbox and
not giving the subject actor time to protest the movement.
* It's implemented by adding a `Settled` boolean to the OnCollide event
object. When the game is testing out movement, Settled=false to give
the actor a chance to say "I'm solid!" and have the moving party be
stopped early.
* After all this is done, for any pair of actors still with overlapping
hitboxes, OnCollide is called one last time with Settled=true. This is
when the actor should run its actions (like publishing messages to
other actors, changing state as in a trapdoor, etc.)
* The new collision detection algorithm works as follows:
* Stage 1 is the same as before, all mobile actors are moved and
tested against level geometry. They record their Original and New
position during this phase.
* Stage 2 is where we re-run that movement but ping actors being
intersected each step of the way. We trace the steps between
Original and New position, test OnCollide handler, and if it returns
false we move the mobile actor to the Last Good Position along the
trace.
* Stage 3 we run the final OnCollide(Settled=true) to let actors run
actions they wanted to for their collide handler, WITHOUT spamming
those actions during Stage 2.
* This should now allow for tweaking of gravity speed and player speed
without breaking all actor collision checking.
* Add the other trapdoor directions: Left, Right and Up.
* UI: Show a color square in each Palette Swatch button in Edit Mode.
* Instead of just the label like "solid", "fire", "decoration" it also
shows a square box colored as the swatch color. The label and box
are left-aligned in the button.
* Minor Play Mode physics update:
* The player jump is now limited: they may only continue to move
upwards for 20 ticks, after which they must touch ground before
jumping again.
* Remove the "press Down to move down" button. Only gravity moves you
down.
* Fix a crash in the Editor Mode when you dragged doodads on top of each
other. Source of bug was the loopActorCollision() function, which only
should be useful to Play Mode, and it expected the scripting engine to
be attached to the Canvas. In EditorMode there is no scripting engine.
