Tower Locked comes from Miroslaw Zielinski.  It's a math puzzle. The objective: delete some of the red circles so that numbers left in each row add up to the number matched on the sides.  Same with the columns.

I have no idea how many levels there are. But the grids go from 4x4 to at least 8x8. That's at level 8, which I did not solve.
The small grids are too easy. The perfect grids are 6x6 and 7x7.  But there's no way to select just those.
https://itunes.apple.com/kr/app/tower-locked/id1173339247"mt=8

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