I love what you did with the music! The art was great. I like the concept as well.
I did feel like it was difficult to keep track of each world. Especially because you don’t know if the platform you are on is safe in other dimensions. Maybe adding a single item from the safe dimensions to the current dimension could help alleviate this. Eg. add a dark item to the light realm on the current platform when they are in both dimensions. Just some food for thought.
Distance while swapping was another thing that was difficult to keep track of. I think this is because of the way that the camera follows you as you jump.
Wall jump felt pretty restrictive because of how long it took away my controls for.
Your platformer could really benefit from looking into Coyote Time/Jump Buffering. There were definitely more than a few times that I died because of it.