Actually it was a pretty good game in terms of gameplay. The mechanic introduction feels smooth, starting from entering the door, you jump out of the door in stage 2, and doors are mixed with the moving platforms in the last stage. The platforms in the different dimension are also telegraphed well, this is a pretty good QoL feature.
I'd suggest showing paths of the moving platforms. In stage 2 I didn't know there was a moving platform on top of the stage so I just did a leap of faith and found nothing, which confused me for a bit. Also the moving platforms suddenly changing direction in stage 4 felt unfair. Showing how the platforms move would solve these problems.