Cool game! Having a speedrun game involve time manipulation mechanics is a very cool idea!
Having to slow down to make sure a cube is placed correctly seemed against the core of the game, which is to go fast. When the levels flowed nicely, it was really fun to blaze through a level, but having to slow down kills the momentum.
The level that introduces the time stop mechanic is brutally hard, unless I was doing it wrong, I had to do it many times before I made it to the door before the time stop ended, especially for a first introduction to the mechanic.
The green boost pads felt a little bit weird, some of which didn't feel like they flowed together and required some weird mouse movements to pull off. I couldn't do the one level with all of them around the large room, just because of how off they felt when jumping on and off of, especially when the first jump felt a bit awkwardly placed.
Lots of potential here for a new take on speedrunning games, having to go down one path, and then rewind to have another path open was super fun! Since it kept the speed and flow of the level going.
Visuals are great, having a weird modernistic feel. Music fits it well too.
Nicely done!