Josh, he does what you make him do with the mouse. You hold down to make him crouch, then move it up fast to make him jump. Move the mouse over to the right and up and he'll frontflip. Then when he's in air, tuck (hold down) to make him spin faster and hold up to slow him down. Slowing it down makes it a lot easier too.
I suggest you download the real version, it's way better. There are a lot more levels, better graffics, full screen, you can make the skis tighter and stuff.