It's insane to me that your team started with a game engine just a few days ago. My mind is blown. I think you managed to actually tell a story and paint a picture of a world which is awesome to see. I liked the level of polish you had with the animations, the sounds and music too! I think a way to improve it (should you choose to keep developing it), is adding more variety with the enemy spawning, maybe more and more appear every few waves to add to that level of tension. It's still so impressive to me that your team managed this with no prior game engine experience. Well done!