This is a neat concept, but ultimately all you have to do to win is fill in all of the blocks, occasionally undoing one to let a square out.
Why is there only 1 level? Why is there only 1 goal shape? Why not have different colored squares and different colored goals and challenge the user to sort like that. Make hazard squares that the player has to trap and keep away from the goals, and if they touch a goal you lose. There's more potential to this game than game itself in it's current state. Give it a few updates and it'd be a blast!