I wouldn't really call this a game as it isn't quite that complete yet but it is a Great game mechanic test!

Slowing the obstacle down works flawlessly but feels a little hollow in general, almost like you're just pressing a button to slow down the obstacle itself rather than time.

I imagine this could be solved by adding a trail on the player and other moving objects whilst slow motion is active and adding some kind of screen effect.

As a game idea you could make a game where theres a goal of how many times you can slow time down to complete some kind of platforming puzzle.

Using this to dodge projectiles would also be awesome. ;)

Hope the feedback helps!