Once I figured out the tutorial typo, I love this game concept. Running around as a speedster feels super good. I only have 2 notes:
The others being on ice when you push them makes them feel hard to control
Honestly, I feel like the greatest limitation of this game is the "only once" aspect. The game gives you the most strategic control when you're in the slow mode, so only being able to use that once, particularly in longer levels, puts you in a position where you either feel inclined to never use it in case you need it later, or frustrated when you did use it and then you can't save them. I think there are better solutions than the "only once" aspect. This has the potential to be something really special. I hope you flesh it out a bit more