Game:
* Neut tileset
* level loading
* Rexx can run over Jaye and vice versa
* drawing queue (tile index = priority?)
* Title screen
* Ending screen

tooling ideas:
* rearrange tile order, preserving maps
 * (needed for Neut tileset? or special neut-ified versions of _everything_?)
* REPLy buffer (Polywell?)
* save player positions & map state during hot reload
* debug movement (noclip? teleport? activate by clicking? MAME supports mouse input / debug overlays...)