Generally a good concept, but there are a few issues:
1. The game is way too hard. It doesn't tell you where the enemies will spawn, maybe just add particles or something, and there is no way to get rid of enemies, so that you will just lose because there are too many enemies.
2. Simple graphics are okay, but pick a good color scheme. Websites like "Coolors" are really recommended.
3. Use a different font.
4. Add sounds and maybe even music.
I hope my feedback helped you, it would be really cool if you could check out my submission too. :)