Rules and Regulations

Objective

The goal of Pentachess is to checkmate the opponent's king. This means that you have put the king in check (danger), such that there is no legal move for the opponent to play that gets their king out of check.

Setup

The game is played on a 90-cell board consisting of 3 decagon rings, with 10, 30, and 50 cells in the inner, centre, and outer decagons, respectively. Each player has 18 pieces, each of which is one of 7 piece types.

Turns

Both players alternate turns moving one piece per turn.

Time Control

Each game may be set up with an optional timer that decrements while it is a player's turn. The timer pauses once it is no longer that player's turn. If the timer runs out, that player loses.

Win Conditions

• Checkmate: Described in the Objective above.
• Resignation: The opponent resigns.
• Timer reaches 0: The opponent runs out of time.

Draw Conditions

• Stalemate: A player's king is not in check but the player has no legal move.
• Insufficient material: Neither player has the necessary pieces to checkmate.
• Threefold repetition: The same position occurs three times in a game.
• Agreed upon draw: One player offers a draw, and the other accepts.
• The 50-move rule: There are no captures and no pawn moves within 50 consecutive moves by each side.

Movement

The rules of movement may be seen for each piece in the next section. For each piece except the pawn, a move includes possible capture. For the pawn and Berolina pawn, the two are different. Just a few notes to properly understand all the notation:

• Orange Cell Highlight: The currently selected cell.
• Blue/Red Cell Highlight: Available cell to go to. Blue is for a move without capture. Red is for capture of an opponent's piece.
• Grey Outlines: Cells that would normally be available to go to, but not in the current scenario, as it would put (or keep) the king in danger.
• Red/Yellow Cell Outlines: Indicates the cell which the corresponding rule refers to.

Pawn (CW/CCW)

The pawn has three types of action: move, capture, and promotion. Each pawn is marked for direction, either clockwise or counterclockwise.

Move: The pawn can move within its decagon one cell across an edge in its given direction. If it is the pawn's first move, it can move two cells forward.

Move: The pawn can also move one cell across an edge into an adjacent decagon.

Capture: The pawn can capture within its decagon one cell across a vertex in its given direction.

Capture: The pawn can also capture onto a same-colour cell across a vertex into a different decagon, if the destination cell shares one vertex with the pawn's originating cell and with the next same-colour cell in its given direction in its originating decagon.

Promotion: The pawn can be promoted (optional) to a knight, bishop, rook, or queen upon reaching the opposite side of the board: any cell from a25 to a32 for team White, and any cell from a0 to a7 for team Black. If promotion is declined, the pawn must leave and re-enter the outer decagon in order to be prompted for another promotion in the given cell ranges.

Berolina pawn (CW/CCW)

Similar to the pawn but with reversed move and capture. It is also marked for clockwise or counterclockwise direction. It cannot, however, move two cells forward on its first move.

The Berolina pawn moves as the pawn captures.

Capturures as the pawn moves and can also be promoted.

Knight

The knight is pretty straightforward, just one rule.

The knight can move onto one cell across a vertex to a different-colour cell, excluding any edge-adjacent cells.

Bishop

The bishop has three types of move; two are simple, and one is tricky.

The bishop can move onto any same-colour cell within its decagon as long as the path to that cell is clear (meaning there are no other pieces in its path). Here, the path consists of all same-colour cells from the starting point to the destination cell.

The bishop can also move onto any same-colour cell across a vertex into a different decagon, and onto any same-colour cell across two consecutive vertices in a straight line (two decagons away) as long as the destination cell has the same orientation as its originating cell, and the path to that cell is clear.

Rook

The rook is not too difficult, just two types of move.

The rook can move onto any cell within its decagon as long as the path to that cell is clear. Here, the path consists of all cells from the starting point to the destination cell.

The rook can also move onto one cell across an edge into a different decagon if such an edge exists.

Queen

The queen's move is simple to understand, assuming you have an understanding of the bishop and rook.

The queen can move as a rook or bishop. This means all available moves that the rook or bishop can make from the cell that the queen is on are legal moves for the queen.

King

Make sure to defend this piece at all costs! Just one rule.

The king can move as a rook or bishop by one step only. In simple terms, it can move onto any edge or vertex-adjacent cell that the bishop or rook would be able to.