Really great style and visually polished entry! The cel-shaded look and lighting is really well done. While I really liked the music track itself I felt like it kind of clashed with the gameplay, as the music is very gentle and relaxing while there is near-constant action happening on screen. The sound effects being filtered and sounding muffled like they're underwater is a very nice touch though! I think it's a great core of a game, and with some minor tweaks could definitely be something that could be published. Some added variety of upgrades and enemy types would be nice to have if you keep developing it.
You can check out my gameplay video playtest below for more in-depth feedback!