Very nice! Particularly liked being able to set my own difficulty - increasing the score if you get to the next gem quicker is a great touch, and led to me dying through greed on more than one occasion.
Visuals were great, with nicely done animation for clouds and gems that added interest to the screen as a whole but didn't distract from gameplay. Also really enjoyed the animation for the title bouncing in.
Delighted you added WASD as per your comments below - just feels so much more natural to me :)