This is really great arcadey feel! Has a very nice shared vibe with the arcade games on the GB. If the lag between movements is intentional, it might be helpful to convey it visually. Also, I reached a point where no more bullet tiles were spawning, so it might be nice to just make sure that one tile on the grid always has a bullet in case you run out, rather than waiting for them to appear. If developed on further this would be a fantastic game to pick up and play for high scores!