Excellent use of different abilities and the level design complements these abilities. Each ability felt like they got to be in the spotlight for each level that they appeared in. I tend to struggle with level design when double jumping is involved, so I tip my hat to you on that aspect.
However, I tended to default to the black cube to use the double jump to scout ahead: the camera was zoomed in too much to determine where the next platform was. This resulted in many a blind leap of faith.
The mechanic of having to move each cube to the end of the stage was unique. I tended to forget to hold it down after particularly tricky sections, which was frustrating as I would need to have to reset the entire level. This proves to particularly noticeable in levels where the rift was behind a door and then a cube is sent back to the previous checkpoint either by death or when I accidentally fat-finger pressed the R key when trying to hit D or T. A possible way to ease this could be to have a zone around the rift that only allows level progression only when all of the cubes are in the zone. My grievances aside, it strengthened the community theme of you game as all cubes were required in later levels and gave a unique identity to the game.
Overall, it has good mechanics and level designs that utilised the the unique abilities of the cubes.
P.S. It was interesting to read your devlog and see how you went about development. I'm still very slow on the development side of things, so it was interesting to see the differences in someone else's thought processes and workflow. I will try to do this in the next game jam I join incase anyone can glean anything useful from my own thought process.