Logic Masters Deutschland e.V.

I have wanted to combine tetromino and chaos construction for a while. I finally came up with this ruleset which I think leads to new interesting logic. Hope you enjoy! If you like mediocre chaos construction, check out my other puzzles!

Solve on SudokuPad

Rules

Chaos Construction: Divide the grid into nine orthogonally connected regions of nine cells. Each row, column and region contains the digits 1-9 once each.

Shading: Shade exactly one cell in every row, column, and region. Shaded cells also contain digits.

Tetrominoes: Divide the unshaded cells into tetrominoes - groups of four orthogonally connected cells. Each sudoku region contains two complete tetrominoes and one shaded cell. Tetrominoes of the same shape cannot touch orthogonally, even across region boundaries. Rotations and reflections count as the same shape.

Shaded Sums: Each shaded cell must touch both tetrominoes in its own region orthogonally. Its digit equals the sum of the smallest digit in each of those two tetrominoes. For example, if the two tetrominoes in a region contain 1, 5, 7, 9 and 2, 4, 6, 8, their smallest digits are 1 and 2, so the shaded cell must contain 3.