VOXEL RACERS

Two devices, one race: a phone, a tablet or a computer each. One hosts, the other scans the code or opens the link -- power-ups and bumping included.

Six cars in a walled arena, three blocks floating over each. The boxes give the same power-ups as a battle race -- missiles, lasers, anvils, smoke, a ghost, a star... -- knock their blocks off. Nothing hits what it can't see: hide behind the walls. Lose all three and you're out: the last car standing wins.