Bright and cheery music, with eerie grass. Love it.
Perhaps give the entities some indicator of death other than falling to the ground. Disintegrating into dust would be cool, but might take too much time...
Also, giving the player a way to regenerate health might also be helpful. At the end of the day, the decision is up to you, but having the player restart for minor lapses in judgement here and there might be a bit too harsh (especially since some of these caves can get quite large). Maybe 1 added health point up to 3 max per level finished?