GemDigger is simple but it works well, the mechanic, progression and challenge obvious the moment you start to play. I think it stuck to the theme well but it also worked against the game a little - my hands were getting pretty sore from spamming the move keys by the time I hit the final layer.

I think it could have benefited from some simple effects to liven the game play up a little - e.g. a dig particle effect, or some simple animations - but overall this doesn't detract from the game's intended style. The music was also pretty cool, a nice touch.

All in all, a good game and I enjoyed it. Well done! Rated.