Slime Volleyball

Controls: A/D to move, W to jump. First to 6 wins.

I asked Claude to recreate Slime Volleyball, the classic 1999 web game. The goal was simple: two slimes, one ball, a net, first to 6 points.

The initial version worked, mostly. Ball bounced, slimes jumped, physics felt okay. But the AI was broken in ways that took a few iterations to fix.

The first issue: during the serve, the ball would drift across the screen whenever the AI was serving. Turns out the ball’s position was locked to the server’s position (so it bounces in place), but the AI’s movement logic was still running. Ball follows slime, slime follows ball prediction, chaos ensues. Fix: disable AI movement when it’s serving.

The second issue: the AI would get stuck bouncing the ball straight up, never getting it over the net. The problem was positioning - the AI placed itself directly under the ball, so the ball hit the dead center of the slime’s curved surface and bounced straight back up. The fix required a shift in thinking: to hit the ball toward the net, the AI needs to position itself so the ball hits the left side of the curve. That means standing slightly to the right of where the ball will land. Add in moving toward the net while jumping, and suddenly the AI could actually play.

These bugs aren’t complicated once you understand them. But finding them required actually playing the game, watching the AI fail, and reasoning about what was happening geometrically. The kind of iteration that makes building games fun.

If you want to try building it yourself, here’s the prompt we used.