Edit: Having looked into the source code... wow! For the "capman" game, he's creating the game map using ascii art and his "help.js" library has a function just for that: asciiArtToMap. This takes me back to the early 90s when making games meant you had to bitblt sprites and worry about every byte in the RAM. His library is great if you want to make sprite-based 2D scroller-type games but I don't know if it is easier to roll your own mini-library or use his for other types of games (e.g. puzzles). However, the source code itself is very extensive and I can certainly see the gamebox.font library being very useful for JS games.