Logic Masters Deutschland e.V.

This puzzle went through multiple revisions - thank you so much ClashCode and bellsita for being the best testers ever!

Rules:

• U-Bahn: Draw a single connected network of lines going through the centers of some orthogonally adjacent cells, which may branch and cross but does not have any dead ends. Clues above and to the left of the grid indicate how many times a given tile, including its rotations, will appear in that row or column.

• Tetrochain: Place some tetrominoes of ice cells in the grid such that no tetrominoes are orthogonally adjacent, but all tetrominoes form a single connected network by touching diagonally. Tetrominoes touching diagonally may not be the same shape, counting rotations and reflections as the same. Shaded cells are not ice cells, nor do they contain part of the u-bahn network. Clues count the number of ice cells in the indicated direction or directions combined, seeing through shaded cells to the edges of the grid.

• Interaction: Ice cells are either empty, straight, or crossing. Unshaded cells are either turns or T cells. Each tetromino must be visited at least once.

• Cipher: Same letters represent same numbers. Different letters represent different numbers.