TODO

* Better file system. At the least, to be able to distinguish relative 
	filenames and to resolve them.

* Maybe a real animation file format?

* Game state type module thing.  Something that can keep track of the overall
  state of the game, and which will keep track of loading the right areas,
  etc.  Also should be able to receive signals from objects or tiles related
  to game state.

* Tools for objects so they can interact better with their environment.  In 
  particular, the ability for the player object to see if it is standing on
  something, and the ability for walking monsters to see if they are about
  to walk off an edge, etc.  Probably move some of the general geometry code
  from collision.c into a separate module so that these functions can use the
  vector/line intersection code and whatnot.  This will allow me rewrite the
  gravity and jumping code for the player so that we can only apply gravity
  if the player is not standing on something -- this way, I could get the
  player walking up slopes without so much difficulty.

* Friction in collisions.

* Improved sound effect system.

* Graphical layers in the maps.  Sometimes you just want a graphic to scroll
  around on the screen, without having to split it up into tiles.  This will
  also involve a little bit of changing to the parallax scrolling code.