How to play

How to play Chessum

Chessum is a logic puzzle played with chess pieces. You get a small board with numbered squares and a set of pieces. Place every piece so that each number equals how many pieces attack its square. When every number is right, it’s Checkmate: the puzzle is solved.

Try it on tiny boards Play today’s Daily

The rules

Two rules first

• Numbered squares never hold a piece. Pieces go only on empty squares.
• A Knight jumps in an L and reaches round corners: a Knight on c2 attacks a1, though they share no line.

Goal

• Place every piece from the set. The puzzle is solved when each number equals the pieces attacking its square: Checkmate.

Numbers

• A number counts the pieces attacking its square. A 0 means nothing attacks it.
• Pieces never stand on a number. A square without a number tells you nothing.
• One piece per square at most. Every puzzle has one solution, found by logic alone.

Pieces

• Rook: along its rank and file. Bishop: along the diagonals. Queen: both.
• Knight: the L-shaped jump. King: the eight squares around it.
• A piece never attacks its own square. Pieces may attack each other. It changes nothing.

Blocking

• A Rook, Bishop or Queen stops at the first piece in its way. That piece is attacked, nothing beyond it.
• Numbers are transparent: lines pass straight through them.
• Knights and Kings are never blocked.

A worked example

Here is the first practice board: 4×4, one Rook to place. Numbers count the pieces that attack their square.

1. A piece only goes on an empty square, so the Rook has three choices: d4, b2, a1.
2. On d4 it would attack c4, which is a 0. Not there.
3. On a1 it would attack c1, which is a 0. Not there.
4. On b2 the Rook attacks c2, d2, a2, b1, b3, b4: every 1 on the board, and no 0. Each number is right: Checkmate.

Real puzzles work the same way, with more pieces and bigger boards: rule squares out with the 0s, then count.

Techniques

Ruling out

Use the 0s to rule squares out: nothing attacks a 0, so the Rook can't stand on its rank or its file.

Two attackers

Numbers add up: a 2 is attacked by two pieces. Find the square that both the Rook and the Bishop reach.

Around the corner

A Knight's L reaches round corners: it attacks squares it shares no line with. Only two squares reach the 1 in the corner, and the 0 rules one of them out.

Counting pieces

Every piece must be placed. One Knight left and one square that fits it: it goes there. On the board you can mark a square X to remember it’s ruled out.

Blocking

A Rook, Bishop or Queen stops at the first piece in its way. That piece's square is attacked; nothing beyond it is. Here a Knight keeps the Rook off the 0.

Shielding

Sometimes a piece must stand where it shields a 0. The Bishop's diagonal points straight at a 0: find the piece that blocks it.

Numbers don't block

Numbered squares never hold a piece, and they never block: a ray passes straight through them.