Grader

Place each letter exactly once in every row and column — the rest of that row/column stays blank. Every puzzle is solvable by logic alone, no guessing.

The rules

• Each letter appears exactly once in every row and column. The unused cells in each row/column stay blank.
• An outside letter is the first non-blank letter you'd hit scanning in from that side.
• Some sides are left blank — that clue just wasn't needed to solve the puzzle by logic alone. Every puzzle is still solvable with only the clues shown.

Controls

• Tap a square to select it.
• With a square selected, tap ✗, a letter, or ? below the board to set it. Tapping the same button again clears it back to empty.
• Press & drag to mark a run of squares as blank ✗.
• Tap Ansatz to explore a possible path. Letters and ✗ marks turn orange while you work; choose Verified to keep that path or Discard to return to the exact board you started from.