Hey, thank you for your detailed feedback! I'm currently trying to fix the framerate issues. Did you play the browser version or the desktop version?
Chrome : By 450k score there is noticeable lag even without slimes or any monsters on the ground.
With a dozen of any mob the fps drops as well.
Spawning slimes from one end of the map to the other also makes it way way worse.
Chest/Upgrade selection screen lags a bit, but not much. Even with a map full of slimes