Great simple concept. The random level generator is a cold mistress though. :-)

Game's pretty good. With a bit more dedication and inprovement can be perferct.

Fun and very addictive.

It would be nice to see it developed.

There is definitely room from improvement and development of this.

The difficulty seems random, and the difficulty doesn't increase. The start sometimes seems harder and progression easier. Maybe change this?

The gems have no purpose for anything but skill manouevering but it'd be good to see them used as currency for updating the drill after a couple of rounds. Diamon drill head and sleeker body etc.

Good game author and thanks!

cool game but you should add a shop because the gems are useless

This is close to being pretty good. It could use some changes.

The terrain generation should be a bit more forgiving up front. Often times, I'll die immediately due to a tiny gap between two rocks. Also, it really shouldn't stop you as much if you're only barely touching rocks. It should do something like the average of the material you're going through. Perhaps having less dense rocks at the beginning would be useful.

It might be worth considering an upgrade system to use the gems for, or giving a speed boost, or drill strength, or something. As it stands, it's hard to tell if they're worth going for at all. Upgrades aren't necessary, but having a better feedback for the gems, even if it's only a a +100 showing up for a moment under the score instead of adding silently to the score, will make collecting them feel better.

The controls don't seem intuitive to me. Since it's rotation based, I keep wanting the controls to be inverted. It might be a good idea to give that option.

Also, if I leave it at the high score screen for a while, it seems to cause terrible lag, which goes away as soon as I go to start playing again, so you might have some leakage going on. If you plan on doing anything more with this game, you'll want to fix that.