This puzzle appears in "Challenge Your Brain Math & Logic Puzzles" (Dave Tuller & Michael Rios, Puzzle Wright Press) as "Eminent Domain".
Puzzle and Goal
An unsolved puzzle consists of a rectangular grid with number clues in some of the cells.
The goal is to draw lines in all non-clue cells to satisfy the clues.
The solved grid must satisfy the following conditions:
Straight lines originate at each numbered cell.
Each non-numbered cell is covered by exactly one straight line.
Each clue is attached to the number of cells in its clue.
As "Mauerbau" or "Walls": Lines are counted for all the clues they end at, rather than just once.
Eminent Domain; Lichtstrahl; Mauerbau; Vier Winde; Walls