I really liked this demo, although I thought it was too short.
Some notes, first the game detects usb controller but won't accept input(linux); I ended up using qjoypad to play with controller and the game was much more enjoyable. I just wanted to verify this wasn't a VM issue.
Second, the boss was very balanced. I thought I had it figured out, then it changes the pattern. I really hope you can achieve this sort of challenge for a full game.