As the game is pretty straightforward, a solution for completing it isn't really needed.
I'm writing this, however, because I was stumped by what an uberwin is after earning one on my first victory.
After you kill the gumball machine, you'll go to the final portal. If you enter, you win the game and earn this achievement.
If you look, though, you'll see you can run behind the wall and there's another portal on that side. When you enter this portal, you'll enter a new level in which you destroy the heart of the tower. This is an uberwin. Hopefully this helps somebody out. Seems strange that you get an achievement for the "easy" ending, but nothing for the "hard" ending.