If I had to make changes...
... to this game, I would add more obstacles and a larger play area. The original difficulty of "how do I manipulate the squares?" decreases with every second playing the game, so much so that by the time the diagonal movement starts, its not so much a challenge anymore as a small mental adjustment. I think 4 sets of squares is plenty if configured properly to be challenging, however I think there could be more obstacles as well. The mines were clever but I never ran into one until invisible mode. In my first playthrough, I actually lost because I though the boxes were not supposed to touch the mines intsead of the cursor, and after completing the game, I think an obstacle that the boxes cannot touch would add a level of depth to the game's difficulty.
I would also increase the playing area, but keep the boxes the same size. The reason I say this is many times, especially near the end of the game, in moving my cursor around to see how the boxes reacted, boxes would collide on random and pair off the screen, which is very unsatisfying.
Overall a great game. Interesting and original, yet a little short, and I think it has a ton of room to build onto it and improve.