The best integration of the theme i've seen so far !! It's a really cool idea and i think if you work on some aspect of your game it could be really great, like the speed of the player (i hit so many snails because i was going too fast haha) also, like other said, the first map size is a bit too big because i was more into searching snail than fighting them (i get the fact that you wanted the reduce the map size over time but maybe begin with a smaller size !!) but otherwise good job
(forgive my english im french)