i liked it, the gameplay is very relaxing, and the audio does a good job.
The image gets a bit blurry on high resolution, I imagine you're using sprites, so make sure to change the "Filter Mode" to "Point (no filter)" in the import settings on your .png in unity, so they should remain crisp when upscaled. (filtering is more commonly used for textures on 3D meshes).
You might find some fun in implementing raycasts for the enemy vision, so boxes will cut the line of sight :D