The .sna file works fine. Level generation isn't bad. But the moment I'm next to a monster, I have to mash the direction keys a whole lot before landing a single hit, and then it doesn't seem to do much. It would be more responsive if it was turn-based, in my opinion.
It is turn based. There's a little indicator in the bottom right of the screen that rotates to show the machine is "thinking". The main loop waits on a key input before progressing. This should be handled by the pause 0 at line 530. Mashing the keys probably wouldn't result in a good experience.
For me the issue is with the amount of entities that can be on a level and the amount of time it takes to process their moves. With a packed level it can be between 20 to 30 seconds between turns.