I think your game is very cool, criminally underrated and for a solo dev, it's very impressive ! I think it's a mix between doom (the og) and vampire survivors so I'll compare your game to them, but I do understand that you worked alone for 4 days ; I gave your game a high grade, it's more if you want to keep working on your game :)

In doom, the best part of the game is not really the combat, it's the freedom of movement and how fast paced you move. the level design is also a big part of the appeal (not the button pressing however, but the verticality) so having obstacles would have complemented the shooting a lot :) 

In vampire survivor, a lot of the fun is from the "high risk/reward" that comes from collecting xp. It probably would have be better to have the enemy drop the token; or some reward to make risk taking more appealing. As it stands, its a really cool game with avenue to improves.

I saw that you wanted to add a tutorial, but I don't think it's needed. I do agree that it is sometime confusing, so here's something you can do to make it less confusing :

- for the eye, I didn't understand as well what they did. Adding a clock to their sprite, with arms that rotate fast around the center of the eye, would probably be very effective way to tell the player what the eyes are doing.

- for the shop, give the player a few seconds at the end of the wave with something like "wave defeated, opening shop in 3... 2... 1..."

Fun arcady game, but I kept getting ambushed from behind. Maybe a directional sound from enemies can help there.

Also I was not sure what the eye is doing, or how to open the shop.

Firstly, I love the style. I am a big sucker for that kind of retro FPS. I've never seen a game with this style where you can jump!

I think the pacing of the game is a little off, probably because of the balancing. It doesn't feel like I am fighting against the pressure of this countdown, it is almost like a secondary thing thrown on top. With some balancing work, I think you could make that feeling of pressure and tension a lot better. The combat mechanics were very well done though, and the art was great. Awesome job!

Love the ideas of mixing 2D in 3D environment. Some improvement I think:

- Need some kind of indicator on the screen to let player know where the enemies is coming from when they're getting close. At some point I got hit by range enemy that I dont know that they spawn behind me.
- I think this is survival genre right ? Maybe we need some landmark in the environment so that player dont feel lost when running around
Overall this is good, there is room to improve ! Kudos!