Neat game. I really like both the lighting and cave generation systems. It's fun throwing glow sticks to light everything up, and finding a new cave with a bunch of crystals is always exciting.
Gameplay wise it's simple but works well enough. One thing I felt it was missing is some way to heal. Maybe there could be a mining material that heals you? Also, having to quit and re-launch the game (unless I'm missing something) to restart is annoying.
Good job overall, though.