You did a great job making the game run with all that grass in WebGL. The enemies feel spongy because they probably have a big HP bar and have no visual feedback or animation when hit.
Viewing post in Operation: Alien RIPley jam comments
Yeah better hit feedback for enemies and for the player are some of my todo list items I didn't have time for anymore. I also wanted to add RPG like stat upgrades so that you can make yourself stronger which would have made enemies only spongy at the start. Maybe I should have changed the balancing.