Pick your contender.
Choose from six letter and symbol shapes. Everyone starts with the same mass and spin speed.
A LITTLE EXPERIMENT IN PHYSICS
Turn letters into
battling tops.
Pick a shape. Find your angle.
Let the collisions do the talking.
THE DOJO / PRACTICE ARENA
O
YOUThe ring
30.0SECONDS
CPU PRESETThe cross
X Ready when you are.0 COLLISIONS
M1 PROTOTYPE Experimental 2D arcade physics, not a real-world top simulator. Balance is still being tested.
A good fight is simple.
ONE ARENA. SIX SHAPES. YOUR NEXT EXPERIMENT.Aim. Launch. Collide.
Set your launch angle and let go. The shallow bowl pulls both tops toward the center.
Stay in. Keep spinning.
A center crossing the ring or a sustained spin-out loses. Still going after 30 seconds? It’s a draw.
The actual rules, not a mystery score
Both tops have a mass of 1 unit, a maximum radius of 0.86 units and an initial spin speed of 17 radians per second, in opposite directions. The computer always launches straight toward the center. Shape mass distribution changes rotational inertia.
The ring radius is 5.15 units. A top loses when its center leaves the ring, or when its absolute spin stays below 1.05 radians per second for 0.9 seconds. If both lose in the same physics step, the result is a draw. A 30-second round also ends in a draw.
This prototype uses a small custom 2D rigid-body solver with compound convex collision shapes. It is not Rapier, and it does not model 3D wobble or precession. Results are experimental. Leaving the browser tab pauses the game; no time is fast-forwarded.
Prototype & privacy
This build has no accounts, payments, advertising, cookies or third-party analytics. Match state lives in memory and resets when the page reloads. The app does not upload matches. Cloudflare hosts this prototype and may process request information to deliver the site.
BumpDojo is a working name. This early prototype remains marked noindex while device testing and release review continue.