Every square has exactly one echo.
Echodoku is a number puzzle with a single rule. An echo is another square with the same number, exactly that many steps away. Left, right, up or down. Not zero, not two.
Tap an empty square to place 1, 2 or 3.
Echodoku is a number puzzle with a single rule. An echo is another square with the same number, exactly that many steps away. Left, right, up or down. Not zero, not two.
Tap an empty square to place 1, 2 or 3.
Fill every square with a number. Each one needs exactly one twin at its own distance. A 1 right next to it, a 3 three steps away. Numbers may repeat, diagonals don't count, and every puzzle has exactly one solution. No guessing, only logic.
A hundred puzzles that start easy and end properly hard. Big grids, room for notes, every solution in the back.