The presentation is extremely nice, and it feels like I'm playing the demo of a paid game. There are a few things that need polishing though, and besides the other things the other comment has listed, I noticed a few bugs.
There's a bit of jittering whenever the player character stands on top of a one-way platform, which is a bit strange, but doesn't affect the gameplay. The top left blocks that are reachable by jumppad on levels 2 and 3 have no collision, which I initially thought was intentional and there'd be a secret up there, but I really couldn't find any, so I'm assuming it's probably an error. If you press time-stop enough times in a row, the total time decreases down to -0.02, and everything is eternally stopped (as shown in the picture), which requires a death to reset. This also seems to carry over if you finish the game at -0.02 and hit continue.
Some suggestions I have are to make it possible to unstop time by tapping the z key while it's stopped (although you might not want to implement it if you're going to use the inability to resume time in a puzzle) and to let the moving platforms keep their color. When I first jumped on it, I thought it was stopped, but the platforms still moved even though they looked the same as everything else that was stopped. Since the player and the platforms both move, it seems like an inconsistency that the player keeps their color but the platforms don't.
Overall, it was a good game, and good luck on finishing developing the game!