Nice looking game/engaging levels to move about in, held back a bit at the end with awkward 'combat'.
-Favorite part is how generally open the levels are, and the platforming doesn't feel too punishing, just fun enough to get about.
-I didn't like the level restarting after completing a bonus room, that did feel punishing, though you might not have been able to save the rooms progress after the transition/had enough time to implement that.
And the way the ore scaled your speed felt a bit awkward (top speed/acceleration, not overall/starting speed), though made sense for the moment in the level where it really mattered-and that was a nice touch.
As others have mentioned too, the spikes could stand out a lot more.