Thanks for feedback!
Yes, if I optimize the code, it is possible to achieve level generation almost instantly. But this is jam, and optimization fades into the background)) Loading hides the generation of rooms, pathfinding corridors and other things)
But the crashes are not very clear. The assembly of WebGL also crashed for me, but the Win version worked stably all the time.
Up to about the 10th floor, the difficulty is minimal, so the balance in the choice of improvements is not felt. The challenge starts after the 15th floor.