Eliminates a number of annoying little hacks by getting rid of
`slide_mode` and instead trusting the terrain, live, like CC2 seems to
do (and Lynx definitely does).
- Players and monsters do, in fact, block each other. The helmet only
prevents death.
- Death happens during collision check, which is the entire reason items
don't save you: you're collided with first! This allows removing
several special cases.
- Spring mining is prevented almost incidentally, by virtue of collision
being checked both at decision time and movement time. It /can/
happen to actors other than the player, but seemingly not blocks.
- Some monsters, whose movement is essentially forced anyway, skip the
decision time collision check. This includes doppelgangers, which is
why they always spring mine.
Also expand the blue key MS compat flag to make keys never block
monsters; allow rovers to pass through score flags; and allow
doppelgängers to pause the clock.
This better matches CC2 behavior and also makes some very common
operations, like grabbing a cell's actor or terrain, way faster.
It also allows me to efficiently implement CC2's layer order when
checking for collisions; thin walls are checked before terrain, and
actors only afterwards. The upshot is that bowling balls no longer
destroy stuff on the other side of a thin wall!
I also did some minor optimizing, mostly by turning loops over an entire
cell's contents into checks for a single layer; Chromium now performs a
bulk test about 30% faster.
Downsides of this change:
- All kinds of stuff may have broken!
- It'll be a little difficult to ever emulate MSCC's curious behavior
when stacking terrain on top of items or other terrain. But not
impossible.
- It'll be far more difficult to emulate buggy Lynx (or maybe it's just
Tile World?) behavior where some combination of cloners and teleports
allow a ton of monsters to accumulate in a few cells. I guess I
wasn't planning on doing that anyway.
Collision now uses bits and masks. The main upshot is that ghost and
ice/directional blocks collide much more correctly, now. And turtles
block fireballs.
Also, monsters can now move over "no" signs, and can trample the player
if she's standing on top of an item.
While I was at it, I finished implementing the "bestowal bow", an item
mod (same layer as the "no" sign) that allows any actor to pick up the
item in that tile.
