This was great! I like how smooth everything feels, and the screen shake effect is really well made.
I really like the fact that it's very simple; every time I see a game with a very simple mechanic and one or two buttons to press, I think about what Shigeru Miyamoto once said about the fact that a good game should not need any explanation, and you implemented this concept perfectly, congrats!
Just a question about how you handled spawning enemies, if you don't mind: do you store the pattern somewhere? is it random? do you have multiple spawner-nodes that know what to spawn and when? I couldn't figure it out from just playing a few times.