I love this game! It's so thoughtful. The mechanic to minimize grinding; the generated maps; the opponents that move around; the interesting spins on hostile Tetris. There are just layers of complexity that were fun to discover. I would like to see my opponent's HP go down as I attack them, but other than that. I suppose you could improve the controls tutorial? But I am not sure how to explain how to improve it, so maybe consult someone for advice. It would also be interesting to make it harder to use the ship, to make it special.
I really like the art, too. It might be too much trouble to clean up the line-art, which is a silly aesthetic thing when your character design is so cool. And the movement! The constant movement really makes the map come alive. Maybe play with the palette? Something cohesive and eye-catching? I think you'll be fine on the colorblind front, but it doesn't hurt to check.
It's such a solid start. I can't wait to see where you go with this.