The dash ability is really fun to use! I found the game a bit frustrating up to that point, though. To the point that I almost quit because it felt like I was wandering aimlessly without really knowing how I was supposed to accomplish the goal - but I muscled through because I wanted to give it a good try. If you plan to expand on the game, I definitely recommend making the objective and the controls a little more clear.
The first thing I came across was one of the floating platforms, and I spent a while wondering if I *should* be able to jump (and what the key for it was). Of course it made sense once I found the first rune, but it would have been helpful at the beginning to see a message like "I've been rendered so weak that I can't even jump around like I once loved doing!"
I agree with other commenters that the tunnels get a bit same-y after a while. But I got the feeling that we were supposed to be able to get lost in them. I think it would be cool if the player was able to place markers of their own on the walls. That way, the game isn't spoon-feeding the player, but the player is able to assist themselves with navigation the way a person might do so in real life.
Overall an interesting concept; the glow skill at the end was an unexpected little treat that felt like it capped the experience off nicely.