I completed it. I like the idea of dark section with very narrow flashlight, though there's probably not that much more you can do with it. Aside from maybe a section with strong directional light and no circular light, so you have to memorize the path and then platform through it without seeing everything.
I died once in the dark section and had to restart, which was a bit tedious. I probably would have quit if it happened again. I think the game would benefit from checkpoints if there aren't any. This also made me not want to grab the light and then jump off the cliff in the far left. I jumped off once with no light and died, but there might be a secret down there that I didn't see.
Falling through the ground when you die made me think there was a hole after some spikes at one point. When actually I probably just landed on the spikes. That was a bit confusing and someone might think it was a mean trick and quit for that reason.
After you get stronger light, it's not really that interesting.
The fully upgraded light is kinda painful to look at when it's not dark. (This is me being more sensitive to light than most people, but also there's no reason not to turn the light down when you're higher up.)
I like the music, but I'm not sure it fits the game that well. The game (especially the early bit) involves a lot of waiting on platforms and taking it slow in caves, while that music feels like it wants you to go fast.