This is a simple "sumo wrestling" video game for two players. It is based on the collisions simulation.
One player controls the blue object using the S,D,F,E keys to activate thrusters. The other player controls the green object with the J,K,L,I keys or the arrow keys. You can hold down a key to keep the thruster firing. You can fire 2 or more thrusters at once. (If the keys don't work, try clicking near an object first - this ensures that key strokes are passed to the simulation).