Walking on stairs gets you to next level
Touching up doc comments
Explicit gob storage in serialization
640 screen size for running on half-screen
Rename bioroid -> hybrid
Remove character classes

They're not pulling their weight compared to the rest of the character build
options in the current design plan.
Spawn player in guaranteed open location
Bresenham line drawing code

Generalized by using function callbacks, which probably makes it kinda slow.