I love the dark atmosphere and Superhot style gameplay. You could make a full game out of this and sell it IMHO.
I'm curious to see what would happen if you had an expanded stage to use instead of just three slots. Perhaps six slots and one buffer of damage for forgiveness to offset the chaos would be interesting to try out.
10/10. Everything just worked here, the gameplay was simple to get going and the atmosphere was perfect. Really I really love the vibe here.