Logic Masters Deutschland e.V.

This is the second puzzle in my '3 Series'.

Starting the creation of this puzzle, I knew that indexing digits can give way to some interesting and elegant logic chains. So I tried just indexing 3's and see where that gets me. I needed some other digits to actually make it work, but I managed to stick to multiples of 3 for those. Have fun solving.

Solve on SudokuPad

Rules:

Normal sudoku rules apply.

Numbered rooms: clues outside the grid indicate the digit which has to be placed in the Nth cell in the corresponding direction, where N is the digit placed in the first cell in that direction.