Cool concept. I like the variety of hidden items which made it fun to dig around to see what I could find. I like that there were different animations for the different ways to die whether it's being eaten by the mimic or having TNT blow you up and destroying the surrounding terrain.
I wonder if it would be better if you could dig while the lantern is being used. Your vision is already limited, so I feel like the game wouldn't lose too much challenge. Having to switch between the lantern and pickaxe so frequently does become tedious after a bit. I think just having the lantern always on and reducing the amount of inputs required of the player could streamline things a bit. I think part of the friction comes from having to reach for the 1/2 buttons from WASD keys when switching items which is physically inconvenient. If you wanted to keep the switching, maybe having Right Click be a toggle would be a better fit?
I would also encourage having the timer during the first few rounds to be a bit more lenient since I kept dying and retrying as I was trying to figure out what was going on.
I would like more feedback on things like collecting the yellow circles. I wasn't sure what it was doing at first. Was I collecting more light? Maybe the UI could explain things a bit better and give more feedback to the player when they interact with things like this.
Overall, nice job! I like the sense of discovery the game offers.