Awesome visuals, great horse sound effects, and fun to play. Like others mentioned, I would have also liked to use the spacebar to jump. I noticed that the powerups sometimes spawn inside walls, making them impossible to reach. Sometimes I would also reach the bubble mini game while going in the direction of spikes, so I would die some milliseconds after the mini game. Saving the personal best on disk would be nice.
After seeing the other scores posted here I couldn't resist going back and trying again: