An interesting game indeed.
✓ Pretty graphics and animations
✓ Good level design
✓ Metroid-vania style platforming
✓ Should be fun in co-op too.
✓ DRM-free build exists! (Humble Store)
✓ Linux support!

✘ Microsoft EULA.
✓ This was once tied to GFWL, which stained the game considerably. Fortunately it's now tied to Steamworks which is less bad.

An interesting game indeed. ✓ Pretty graphics and animations ✓ Good level design ✓ Metroid-vania style platforming ✓ Should be fun in co-op too. ✓ DRM-free build exists! (Humble Store) ✓ Linux support! ✘ Microsoft EULA. ✓ This was once tied to GFWL, which stained the game considerably. Fortunately it's now tied to Steamworks which is less bad.