Making progress on map generation.
It's a really cool approach I saw someone mention on the Pico-8 forums a while back, where you use a random set of unfilled rectangles to generate hallways and rooms with interesting obstacles automatically. For my game, islands are also a bonus feature, because continuity is not required when you can lift the water to make more land.
This algorithm is optimized by drawing rects directly on the screen with a special fill pattern, then copying that region to map memory for a direct tileset render (you can see that the CPU usage at the top never ticks to even 20%!). Up next is orthogonal screen connection and permanence, by calculating seeds from the current screen's x,y coords in the global map, to keep save data low (I'll need most of it for spell storage later).