The two separate worlds for when you're alive and you die is a great idea. I do have some feedback:
- I felt that the tutorial area for the shooting range was a bit long.
- There's a lack of feedback on the gun when you shoot. You said that these were placeholder assets and I can understand that. But in a game where the gun is your only interaction with the enemy (for now anyway), making the gun the star of the game is important.
- I never switched away from first person. For one, I forgot the key to do so, and also I feel like it's a better game in the first person.
- I didn't know what was killing me during the horde trials and I figured out it was the water. You should make the water, green, or red just to make it obvious to the player that it's dangerous.
Overall a great start and a lot of work done in 10 days. Nice!