Thanks for the feedback!
I made the scoring system such that Mr. Cube will score a point for each ball he pushes off the edge. However, if one ball fell on his head, he loses 5 points, which will result in a net loss for each wave of balls. It is not a perfect system, but it does prevent him from scoring very high.
And yeah, I worked a lot on the AI of Mr. Cube :) Glad you liked it!