Its a "match-3" game, not that much that I can comment on that design. If anything, extremely impressive to have it finished within 3 hours! Feels ambitious :O
The goal is rather strait-forward with the point barriers and like the bonus move intensive you have with the crystals. The point-balance seems fine if, even if I find it difficult to see how anyone can reach the higher scores. However, I do feel the explosives are way to punishing. 1000 points feels like its a lot and it often felt the screen slowly got covered in the stuff, making the entire higher point gain all down to luck. Luck is unavoidable in mach games, but combined that you can get punished rather harshly just felt quite bad.
I also would have liked to see a bit more variation to the art of the rocks. all the rocks have a very similar color pallet, making you almost have to squint at times to know what needs to be matched. If the rocks have small gems stuck in them, why not use more variation on there colors?