Chess80: Il Ducato

Chess80: Il Ducato is a two-player game and is very similar to Orthodox Chess. It introduces a new piece called the Duke (see below) while all other pieces move and capture like their counterparts in Chess. Chess80 aims to break the mold of traditionnal Chess by offering a fresh new way of playing the game. This novel format encourages creative thinking by not relying on existing theory such as extensive opening databases and memorized endgame tactics. It also strives to preserve balance between complexity and game length in order to reduce the learning curve and to make the transition from traditional Chess as seamless as possible.

Interactive board

Pieces

The Duke

The Duke is a leaper piece. It can move one squere in any direction and can also leap two squares in any direction. The Duke captures as it moves. Other fairy pieces that have the same movement are the Mastodon and the Squire.

In Algebraic notation, it is represented by the letter D.

NOTE: The circles represent a move to an adjacent square and the triangles a jump.

Rules

Generally speaking, aside from the Duke's movements and the expanded Castling rules below, Chess80 mechanics are idential in all aspects with those of Orthodox chess. This includes checking and checkmating, Pawn promotion (may also promote into a Duke), en-passant, 50-move limit and stalemate after threefold repetition.

Castling

Because of the wider board, and to allow for more King-Rook placement variability, castling in Chess80 is very similar to a concept called Flexible Castling first introduced by Fergus Duniho. In Flexible Castling, the King may move two or more squares towards the Rook, while the Rook leaps over to the square immediately on the other side. Additionally, in Chess80 the King is also allowed to occupy the corner squares of the Rook (see examples below).

Restrictions

1. Initial positions: Both the king and the rook involved in castling must be in their original starting positions (e.g. the king on e1 and the rook on a1 or j1 for white) and have not moved from those squares.
2. Empty path: All squares between the king and the rook must be empty.
3. Not in check: The king cannot be in Check at the time of castling.
4. Safe passage: The king cannot pass through or land on a square that is under Check by an ennemy piece.

King-Rook swap

The King may move two (2) or more squares towards the Rook (including the Rook square itself). The Rook is then leaped over to the square immediately behind the King. Castling notation is very similar to that of Orthodox Chess: King-side castling is annotated as N-N and Queen-side castling is annotated as N-N-N, where N represents the number of squares moved by the King. Note: in Orthodox Chess these are respecively written as 0-0 and 0-0-0.

Thus we can see below all possible variations:

• 2-2: King-side castle of two spaces
• 3-3: King-side castle of three spaces
• 4-4: King-side castle of four spaces (lands on the Rook square)
• 2-2-2: Queen-side castle of two spaces
• 3-3-3: Queen-side castle of three spaces
• 4-4-4: Queen-side castle of four spaces
• 5-5-5: Queen-side castle of four spaces (lands on the Rook square)

Example: 2-2 and 2-2-2 castling

Example: 3-3 and 3-3-3 castling

Example: 4-4-4 castling

Example: 4-4 and 5-5-5 castling (landing on the Rook square)

Notes

Design considerations

Movement and placement

The initial consideration was to make the Duke color-bound like the FAD and thus provide a new piece that strikes a balance between the Knight and the Bishop, bringing the total number of leapers and color-bound pieces to two each. While this may seem more intuitive at first, it has some drawbacks:

1. Because of the larger board size, a minor piece like the FAD would not be as powerful and would lead to longer, more drawish games. Same could be said for the WAD (Champion), although the WAD is a tad stronger since it's not color-bound.
2. A King and a FAD cannot by themselves mate the opponent's King. Thus endgames need a 3rd helper piece other than the same-colored Bishop.
3. If there are two color-bound pieces (e.g. Bishop and FAD), there's a risk that both pieces of the same color are captured, thus leaving the player with a double disadvantage. While this could lead to a strategy on its own, it rarely produces a fun game.
4. The Queen and Rook are even stronger on a 8x10 board. The current version of the Duke is not colour-bound and controls 4 more squares, thus bringing it closer in power to these two pieces.
5. At the same time, we know from Capablanca chess (and other similar variants on a 8x10 board) that new pieces like the Archbishop and the Chancellor tend to overpower by the sheer number of squares they control, leading to imbalanced and complex games. These pieces are also complicated to grasp for novices, thus preventing wider adoption.
6. By placing the Duke next to the Rook, the following issues with Orthodox Chess have been resolved: (a) the Rook is no longer unprotected. The Duke-Rook pair protect each-other. (b) A Knight exit to the 3rd rank is protected by the Duke, whereas in Orthodox Chess, if the Knight is captured, one must break the Pawn rank and double the Pawns on the file where the Knight was (c) the Bishop is also protected by the Duke if exiting on the 2nd rank towards the edge of the board, commonly known as Fianchetto. In Orthodox Chess, the Bishop would be on the Rook diagonal and the Rook would not be able to protect it, often leading to the Bishop being captured followed by the Rook itself. This is seen mostly in novice games, however it is an ongoing problem with the orginal setup.

Board size

Given that Orthodox Chess is also played on a square board, why not use a 10x10 board which seems a more natural choice?

An 8x10 board has many advantages:

1. The overall proportion of pieces vs number of squares is preserved to exactly half. 32 pieces vs 64 squares for the orthodox chess and 40 pieces vs 80 squares for the 8x10 board.
2. The 10x10 board leads to longer games and tends to delay initial confrontation.
3. Some pieces like the Knight become weakened.
4. Another advantage of the current setup is that most Orthodox openings involving files 'C' through 'H' can still work. Of course once the Duke is brought out, things no longer work as they did previously.
5. Fits rather well on a smartphone in landscape mode.

Controlling squares and relative value of pieces

Below figures are estimates and take into account the larger 8x10 board.

Some things to keep in mind:

1. The Knight is slightly less powerful as it needs more lateral movements to go from one side of the board to the other.
2. The Bishop has the exact same strength as in orthodox Chess since diagonals remain the same.
3. The Queen and the Rook have slightly more reach on a 8x10 board because of the increased files.
4. The Duke's value should be higher than a Rook's because it can leap (can't easily be boxed-in), placing it somewhere in between the Rook and the Queen.

Last revised by Alex Damian.