TODO:

movement -- note these are hard due to limitations of the Apple II keyboard
+ ability to run
+ ability to jump
+ ability to kick while crouching
+ ability to shoot

sprites_to_draw:
+ physicist jumping
+ physicist hanging on rope
+ physicist swimming
+ physicist getting out of pool
+ beast tripping
+ physicist putting hand up
+ physicist shot backwards
+ physicist holding gun
+ physicist shot

pool:
+

cavern:
+ slugs on ceiling drop

underwater:
+ add arrival-underwater scene
+ ability to swim

beast:
+ add beast death cutscene
+ add beast tripping

rope_room:
+ ability to swing on rope in rope room

cutscenes:
+ death by beast
+ aliens shooting beast
+ aliens shooting physicist

Intro:
+ Implement it?

Level/Checkpoint #2:
+ Intro movie
+ Swing in the cage
+ Ability to pick up gun, with all that entails