131! I quite enjoyed this. Well polished. Simple. A solid entry.
Some things I think could be changed, though I'm not sure if they'd be improvements:
First, the little creatures were pretty simple to capture en-masse when they pushed up against the walls. I think they are just moving in a line away from the player, but steering behavior might lead to them not bunching up in corners as much.
Second, there were times where I felt like I died because there weren't enough spawning or I couldn't find them fast enough. If I lose, I'd like it to be from my inability to capture the critters rather than their sparsity. Perhaps there's a way to ensure there's always a creature reachable if one plays optimally?
Third, creatures sometimes spawned in front of me. Not a huge issue, but finding them just outside the line of sight can be neat.
Good work.