slush.io

Description:

Slush.io is a free online race and io game. Welcome to the great big race in the sky where you can make your very own custom courses and go nuts. This is a platform based racing game where you can create your very own custom race tracks by simply drawing a few lines.
W,A,S,D or Arrow Pad: Accelerate, balance forward or back. Use your mouse to interact with the in-game menus to create your own custom tracks.