The visuals are nice with some cute critter designs. Sticking to the shadows is a really nice idea and tying it to mechanics was really cool and easy to understand. It's a really nice world you've got, reminds me of the platformers I used to play back in the day :).
I had some issues where I thought I was in shadow but was starting to take damage, it would have also been nice to have an visual effect/sound when the state of being in shadow changes. I know the damage effect starts to show but to really drive home that state changing. That might just be me though.