Doesn’t this grid look like the Tower of Hanoi puzzle? I’m going with that because Fisher-Price seems to market “Rock-a-Stack” under different names around the world, even though I colored the cages and now the pyramid regions look even more like the Fisher-Price rings/donuts.
Rules:
Normal Irregular Sudoku rules apply. (There are nine regions of nine cells each, but they are not 3x3 squares.)
Digits within cages sum to the total in the top left corner of the cage.
Anti-king: Diagonally-adjacent cells do not contain the same digit.
Estimated difficulty: 2 out of 5
Solve on SudokuPad