Not bad! I like the Flash-back (get it) style with its characteristic campiness. I definitely feel like there's a little polish that needs to be done, though, or at least some clearer explanation of what certain things do. The things that weren't intuitive to me were the distance meter at the top, the presence of stalactites and stalagmites as obstacles when they looked more like background objects, the requirement of keeping your headlight going, and the fact that slowing down is detrimental (or at least I think it is - I'm not exactly sure how it affects things). I also feel like the large size of the obstacles and player with respect to the movements makes things somewhat harder to avoid. The stalactites also seem to do no harm if the player is jumping through them.
Other, more miner (hehe, get it) things include the text going off the sides of the "About" background, the fact that if you pause and play the audio in the options menu, the audio plays back panned to the left until you go back to the start screen, and the fact that the skull pile explosion animation seems to replay again in a different place in some situations(?)
Otherwise, I love the creepy-campy aesthetic and the setting/premise. The idea behind this is very fun, and I'd love to see where this goes from here.