Normal sudoku rules apply. Standard killer cage and X-sum rules apply. (Digits in a cage must sum to the little number in the upper left, and may not repeat in the cage. The number in a circle outside of the grid indicates the sum of the first X digits in the row or column, starting next to the circled cell and moving away from it, where X is the digit in the cell closest to the circled digit.) I think this puzzle is 1.5 stars out of 5 for difficulty for many solvers (if you are familiar with the rules). As always, comments welcome. Thanks!
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Solution code: First row of puzzle.