Logic Masters Deutschland e.V.

Rules

Standard Sudoku Rules apply.
Double Decker Sandwiches: In this puzzle, digits 1, 5, and 9 are crusts. An outside clue gives the sum of the digits sandwiched between the two closest crusts to the clue in its row or column.
Quadruples: There are circles in the grid which occupy the corners between some cells called quadruples. Digits in the circles must all appear at least once in the cells touching them.

Sudokupad

This puzzle was set in 90 minutes as an entry in a speed setting tournament organized by dumediat! As such, it’s not as tight as it could be, but I was just happy to finish setting in time. I was knocked out by Niverio’s lovely puzzle: Eight Layered Sandwich