Fun concept! I feel like this was intentional/planned, but it was interesting to see that only being able to select boxes that you can see (with no way to shift the camera) made the decision-making for what boxes to link and which one to be the base of everything tricky (in the sense that you could softlock yourself out of being able to deselect a box if it's not close enough), especially with Level 3.
A very small nitpick, but perhaps the level mechanic that lets you pass through walls could be renamed to something like "power level" or just "power" to distinguish it from the levels in the game.