Loved the music, SFX and the gameplay! The upgrade loop is really good. The only improvements I would suggest are:
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The drill mechanic is a bit confusing. I feel highlighting the cubes that can be drilled when placing the mouse is better than the small yellow dot. Or make the drill affect the near blocks to the player, even if not placing the mouse on top of them. Adding a small driller SFX loop when clicking would be nice as well :)
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Another small nice touch would be that when you die because of running out of oxygen, adding a small animation of the alien emergency warping out of the cave before going out of the cave.
Great game! Keep it up :)