Thanks for playing and for pointing this out :) You were right, and it helped me find the real problem. Every body lying in the grave was its own draw call, so the deeper and fuller the grave got, the more the browser had to work. In the next update the whole pile is drawn in one go, along with a bunch of other optimizations. In my tests a full grave now needs about 2.5x less rendering work, and the game no longer slows down as the grave fills.
If it still stutters for you after the update, let me know which browser you’re using and roughly where it happens. That would help a lot. Thanks again! 💀