This is a standard Killer Sudoku that has been divided into coloured cells. Cells of the same colour must also contain all the digits from 1 to 9. Variants of Killer Sudoku are quite challenging to compile; these puzzles are from Philipp Hübner.
Place a digit from 1-9 in each empty cell so that each row, each column and each 3x3 block contains all the digits from 1-9. The digits in each inner shape (marked by dots) must add up to the number in the top corner of that box. No digit can be repeated within an inner shape. In addition, the grid is divided into coloured cells. Cells of the same colour must also contain all the digits from 1-9.
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