Nice game! I had some troubles with the difficulty whilst playing at first and it was a little bit annoying to have to move the mouse over to the small square before I'm able to move it around - did you try making it so the blue character just follows the mouse itself instead of an object which the mouse has to pick up and drag?
Otherwise, lots of nice content and there's clearly lots of good ideas you have for this idea going forward, I'd be interested to see where you take this idea next (I've said this for a few games already but this could be a really good game to fit on a smartphone format if you are considering looking into that?)