It's a great concept, but it didn't feel super intuitive, though I have a tendency to skip text instructions, and come back to read it first when I get stuck.
The loading minigame seemed hard to understand at first, but after reading the instructions it felt nearly pointless.
The gameplay was slow and not that interesting, though since it's a shooter it should be pretty straightforward to make it more fun to play, shmup is a very mature genre, and there are countless great games to take inspiration from.