Deborah Andrews

Worlds Hardest Puzzles Deborah Andrews

Sign In is played on a square grid. The goal is to fill in each cell with numbers from 1 to N, where N is the size of the puzzle's side. No number may appear twice in any row or column. Some digits may be given at the start. If absolute difference between two digits in neighbouring cells equals 1, then they are separated by a sign "+" or "-". If a border between cells contains a sign "+", a digit in a left or upper cell is one lower than a digit in a right or lower cell. If a border between cells contains a sign "-", a digit in a left or upper cell is one bigger than a digit in a right or lower cell. All instances of consecutive digits are shown by these signs.