An excellent puzzle game! Really had to stop and think for some of those later levels. I can tell a lot of thought and work went into the level design š
The implementation of the theme was really nicely woven into the puzzle mechanics and design too. Having the checkpoints effectively transform the level layout based on how you move around, and having to plan ahead to cross back over your path is super cool.
I really appreciate the skip level button too, as I had to leave and come back, and was able to continue where I left off using that š
An undo button is only feedback suggestion I had in mind, and can see that's already been addressed in other comments.
Great submission!