TODO:
- ammo, fuel
- improve level class
- scenario class/obj
  - map of caves
  - cave extermination dependent actions
  - text info
- sounds / sound class
- new alien classes
  - steam beam
  - alien brooder
  - turret
  - brain
- better sprites
- paralax scrolling bg???
- improve alien motion (pathfinding?)
- path evaluation could be used in level generation? (alien positioning)
- weapon class/es

DONE:
- change player motion
- graphics rewritten using asciiart lib
- animated sprites
- player x monster collisions
- monsters x missile collisions
- status bar
- better tiles
- proper shooting
- some test sprites
- player x level collisions
- scenario class/obj
  - menu