The art and ambience is cool, the sounds with reverb are a nice touch to add to the cave atmosphere. Theme is implemented and it is original.
Gameplay is not bad, it's a good base, but I feel it could be improved a bit? Please don't take it the wrong way, it's all constructive criticism and all those things are easy to fix.
The falling block mechanic was hard to understand at first, I had to die a lot until I got it (white falls no matter what and black non-attached horizontally will also fall) but it's not intuitive right away. Maybe a small tutorial at the beginning of the falling mechanic would help a lot because it's actually a fun part once you figure how it works.
The lamp and its limited visibility to be honest is more annoying than difficult. It doesn't let you fairly decide which blocks to break and it doesn't let you enjoy the falling mechanic since it would be fun for the player to figure out which block to strategically break first (like a puzzle), but first they have to see the whole picture. Maybe increase the radius of the lamp?
Progress is a bit slow, too many upgrades and too few levels, you either finish with a strong pickaxe but super slow, or fast with a weak pickaxe (since lamp is basically mandatory or you won't finish the levels on time). So maybe increase the prices so you can buy all the upgrades by the time you reach level 6?
Level 6 difficulty spiked and I agree with someone else who said they got lucky to find the chest, it felt more like I got lucky I semi-randomly chose the right blocks to destroy and I was like "Oh, ok, I won I guess". I didn't feel like I earned it.
They're not game breaking and as I said, they can easily be fixed and the game will feel a lot more smooth and satisfying. But you did a great job with the rest of the game, I enjoyed playing it and I'm hoping you add more content to play it again!