Unfortunately, it looks like the native drawImage method, which I much-praised last time, also acts as a bottleneck to the whole application. I'll surely need to cut the resolution to a fraction of the window size, probably to a fixed one. On the bright side, that's not a big deal, given how young the project is.
Speaking of bright sides, I've finally got to the point where I move the camera instead of the grid. Borrowing some code from my past self sped that up a lot.
Next up: lower resolution; pause/play states.