Interesting concept! Everything is working really nicely but some art would help a lot! You could consider using open source art assets or even having AI help make the art. The round end screen works really well. It's great to see that you already have something setup for upgrading weapons. It would be fun if the animals interacted with each other and the level in a more interesting way. I hope you keep working on this and consider arting it up. Also you can use the release build of littlejs to prevent the escape debug feature and it runs a bit faster! Great work!