I really like the pixel art style. Everything is really endearing and pleasing to look at. The game drops you in without too much faffing about, as an arcade game should.
One rather major issue that sort of feeds into everything else, you have a bunch of tutorial messages pop up that you expect the player to read at the same time the lava starts rising, so there really is no way to actually learn the controls before instantly dying. And then your energy runs out almost immediately and you get swarmed by half a dozen bats that take several hits to kill. The game should NOT start out this brutal. Tutorial messages like "proximity to lava restores energy" are useful, IF the player could actually read them and wasn't so focused on the hundred other things being thrown at them.
There's definitely potential here, but it is really rough as is. I think the biggest problem is forcing the player to use energy for both flight AND grappling hook, because as others have stated, you're basically already dead because of the BILLION FREAKING BATS THAT TAKE MULTIPLE HITS.
The only way to beat it is to play in a way that's not fun. You want to outrun the lava. That's the entire point of the game. The story encourages you to do it, but then you're punished for doing so. You're forced to hover close to it in order to restore your energy, which I think should be an advanced tactic, not a required one.