Pretty cool concept! The game feels very polished, and can be improved in many ways too. I feel like the enemies should emit some kind of visual effect when they appear, because right now they just pop out at the top without a sign. About the creative use of assets, the game has some good use of the assets, especially the UI, but I feel like you could've gotten more creative with the gameplay, to make it more engaging and fun too, e.g. make some enemies come from different directions or patterns, that could be very interesting in my opinion!
Overall, I think you did a good job with the game!