I especially liked how the sound design gives a strong feeling of being in space. The idea of using a wave to defend is also creative and fun, that said, there are just a couple of small things I personally felt could improve the experience. First, having a short guide or tutorial would help new players understand how to play more easily. Second, adding an exit or quit button after defeat could be helpful for players who want to exit the game quickly.
As for potential improvements, I think introducing stages or wave based challenges could be really exciting, for example, defending until a certain score to clear a wave and then progressing to a tougher one. It could add an extra layer of challenge and progression for players.
That said, even in its current version, the game is already very enjoyable and has a strong core.