An abstract input state object that gets fed user
events and updates itself based on a set of key
bindings.
Basic particle system.
The Scene system is basically for transitioning between
completely different states that have entirely different game
loops and but which all share a state. It operates as a stack, with new
scenes getting pushed to the stack (while the old ones stay in
memory unchanged). Apparently this is basically a push-down automata.
An efficient way of drawing images composed out of tiles from a spritesheet,
such as oldschool RPG maps.