Awesome 3D Skateboard game!
Steer you way down the run using arrow keys - up key activates boost. Click Z and an arrow key once to start GRAB then any arrow key to release. Click X and an arrow key to perform a Battle Board Trick. Pulling off movies gains you extra boots.
Challenges: slalom - collect enough icons to unlock the next slalom run; freestyle - pull off movies and score enough points to unlock the next freestyle challenge; Battle - takedown every opponent before you get hit to unlock the next battle run.