TODO
====

* Changing areas

* Items

* Inventory

* Puzzle objects
  - How much state do we save to avoid breaking the game?

* Game saving
  - still needs to be worked in

* Enemies
  - Are desirable

* Shooting
  - Follows from enemies

* Breakables
  - Has implications for saving state

* Outstanding art:
	* More aliens (how many?)
	* bullets (alien acid spit and human bullets)
	* Weapons which can be overlaid with the protag's sprite in different positions?
	* Protagonist facing N, S and SW (already have W and NW). Rename to cardinal directions.
	* Two of each of these (human and alien design)
		* floor tile
		* door
		* sensor (1 done)
		* indicator (1 done)
		* pushable obstacle (1 done)
		* smashable obstacle?
		* tiles for different surfaces? e.g. damaging (pool of acid), slippery (ice), sticky (alien goop), etc..