Click and drag to draw slopes, then press space. The ball will drop at the grey circle near the left side. Use the arrow keys to roll the ball as long as it is touching a slope. (Note that it's a little buggy/laggy.) Try making a loop and rolling the ball through it. It's pretty awesome.
As suggested (along with my own goal), I made a version of Rolling on Slopes where you can draw things in with pen. It's just a rough prototype for now, but it works well, so I'm sharing it anyway. :)
