This game has really strong atmosphere... The retro FPS style with the eye watching from the sky is really cool, reminds me of Devil Daggers in a good way. Shooting feel satisfying and the music fits perfectly with this quite intense mood.
I noticed the flying skulls are a bit easy to avoid since focus is naturally on the eye above, so maybe if some skulls attacked more aggressively from different directions it could add more tension. But for a 4-day build this is really impressive work, congrats to you!