Great entry! I love the minimalism of the main mechanic: It implements the concept of scarcity in a very concise manner. I wonder if the game would have been better without the instant death though, having a single bullet is enough to feel the scarcity in my opinion. Maybe two or three life points.
Also, having the gun change color or whatever to give feedback that the bullet is already fired would be a great addition.
Very strong sumbission.