Really well executed. You went for the route of a lot of constraints and made a great game, congrats!
A couple of things I noticed as constructive feedback; the power-up marks are a little hard to see and differentiate, perhaps using brighter colors would help. When changing the flow of time it would maybe make sense for obstacles to disappear completely if you can walk over them, I got mixed signals. In the last level you don't seem to need the ghost power up :b
Would appreciate it if you could check out and rate our game, a top-down-shooter/puzzler hybrid where you can absorb only one bullet shot by an enemy of a specific type, and shoot it back. Bullets can bounce on walls and other enemies of a particular type so all levels can be beat with one shot ;-)