It gets really boring and repetitive. I put it on hard mode, and it's still very easy to beat. Just takes two seconds longer to figure out. You should have added somthing more than portals, like movement tiles that move it a certain way automatically when it steps on it, mabye even a tile that moves it a certain way when it approaches it from a certain side , you know, with arrows pointing from the bottom to the left, and from the top to the right. Anything more you could think of. And, I think it's best if you made it impossible for the ball to attempt to move past the outside walls. On a 'Hard' mode puzzle once, it gave me all down arrows when it was near a south wall. Took me half a second to figure out that it wasn't going anywhere.