While the idea seems obvious, the execution is quite interesting. The first 5 puzzles make good use of exploring the concept in a way that allows the player to begin getting a bit of a grasp on the game.
However, the difficulty curve of this game is extremely steep. Making a puzzle game myself, I realize that puzzles are quite difficult to design (especially in a week), but interactions should be more gradually introduced. Once I hit level 6 I felt like I just hit a brick wall. I still can't even beat it (is it even possible?).
Additionally, it's not very intuitive which character does what. While they are opposite colors, there isn't really any basis to go off as to which is meant to be the "opposite." Though by level 5 I felt more comfortable, it made the first few levels difficult to enjoy as it felt more unfair because of it.
Overall great use of the theme, and a good starting place for a game. Would benefit greatly from some more intuitive designs and maybe a hint system.