The core gameplay of fast movement, fast shooting and grappling felt pretty good. The choice BG music is fine as well. But there are some caveats that I must list:
1. The camera placement was not apt fully. Often I was on the ledge and not sure what was below, and there was no way for me to check below, either by mouse or pressing in down direction. This lead to some pretty undeserving death where it was not even my fault. In this way the game essentially plays like you just dying in pits so that if you MIGHT remember the location of the pit where there were spikes. Takes the twitch fast paced action out, down to a full a halt.
2. There were enemies who were lying on their side like they were dead before I had even shot them, or another guy collided with them. Maybe intentional, or maybe not. But the first few times these sidewards lying guys shot me, it was a little hilarious. Not after a dozen times, especially when a few of them LITERALLY fell into the spike hole and kept shooting.
3. A minor one, but whenever the spinach music played, it always played on top of Hedwig's theme. Not how music should be.
Other than that it was pretty good, the on-spot slow mo sometimes was amazing, and the grapple gun gameplay was tight. Overall, good job.