I love games like this. I think people are just too used to straight-forward games that are easy to beat...
To those who are having trouble: "Levels" aren't meant to be fully beaten. What you should do is to first gather stone to protect yourself. Sure you need damsels and treasure to really increase your score, but it's not worth it if the integrity is too low or if there are too many monsters. Make sure there's always an easily accessible escape route in case of a cave in. Also make sure to quickly plug any floods (both water and lava can own your face).
There are some pretty important tweaks to be made, though: Firstly, the player hitbox should be a bit smaller. It's unreasonable for him to die from a fraction of a pixel's length scrape against falling gravel. Secondly, there should be a bit more contrast between dirt wall and dirt ground textures. Thirdly, there should be a pause feature.
I think it'd be nice if wild beasts with a lot less levels didn't always attack.. Other than that I don't think there's really too much more to nitpick that hasn't already been mentioned. Nice game C:
 "Caved In 2"){kind=icon}
 "Pause Ahead"){kind=icon}
 "Lakeview Cabin"){kind=icon}
 "Epic Battle Fantasy 4"){kind=icon}
 "Bullet Heaven"){kind=icon}
 "Outernauts"){kind=icon}