I've not written this sort of gaming code, so this is just guesswork...
Maybe a first (relatively easy) way to investigate might involve compiling that Arduboy code with small changes to increase the map size, while watching the memory usage...
So I was thinking up some ideas of what to make with the Teensy 4.1 that couldn't be done with a normal arduino, and I thought: rougelite? Near-infinite replayability? That sounds cool! Now I know that there is this, which is on the Arduboy which...