It's fun, challenging, and feels good to play. It looks spectacular, giving you cool and intricate bullet hell patterns in a 1-bit style. The music choice is also really good.
The only suggestion I have (aside from just more) is that the difficulty spikes once the patterns become based around melding together to switch colors/destroy themselves. It might be better to introduce easier patterns with this design before getting to the more difficult ones. Also it might be better to have the "warning" icon show up a little earlier than it does for some attacks as it doesn't give you a whole lot of time to react. As the game is designed though, it doesn't detract from the game too much as dying doesn't feel bad.
I really liked the feeling of completing each challenge, especially when I ended up dying to a pattern several times. I also really liked the small portion that had timed switches on the player. It was like a small rhythm section which was cool.
I really enjoyed this entry, great job!