The art is great, the music is bearable, and most importantly, the gameplay is fun. The motion feels smooth! I think there could be more variety for the fish, but for a game made in 3 hours, I believe you did brilliantly! Good job!
It is a very interesting game. You can easily spam and not move and still win, but I think the very concept itself is interesting!
Like I said, it can be a while for mutations to rise, but it has a lot of potential if other features and obstacles are added. Sometimes I also feel like there are too many shapes to keep up with and getting rid of them takes a while, too. Overall, I had a lot of fun!