Chess board

Each value is either a number set here or a reference to a decided number in your tuning. It cannot reference an open number.

A rule is a check between the numbers. Validation reports a rule that fails.

• cell-size >= 0

Each list holds the rows this adoption supplies. A list can be empty.

Some tests need a scope or seeds from the adoption before they can run.

The contract comes with 22 tests. A test that runs once per row is counted once for each row. Tests that do not apply to these answers are still listed, with the reason.

Answers you try on this page do not change this file. To change an adoption, open it in the authoring tool.

{
  "contract": "grid-and-direction",
  "version": 2,
  "origin": "https://opengdd.org/contracts/grid-and-direction-2",
  "summary": "This contract covers square grids and the direction words that your game uses. It says where numbering starts, which cells touch, and how a position belongs to a cell. It says how rules measure distance, decide a tie between two cells, list cells in order, and turn. This contract does not cover grid edges, pathfinding, cells that are not squares, or a third axis.",
  "mechanism": [
    "The mechanism is one grid of equal square cells. A row runs across it, and a column runs down it. When a game names a cell with two whole numbers, coordinate-order says which one comes first; a layout may name cells by their contents instead. The grid may be a bounded rectangle with a first cell in one corner, or continue in every direction with signed numbers and no first cell; the first question says which.",
    "This paragraph defines the grid's own frame. Every answer below refers to the grid as this package declares it: the layout your content writes out, or your own chapter's sentence about which way the numbers grow. Up, down, left and right mean those directions on the declared grid. On a bounded grid where content writes the grid out row by row, the first written row is nearest the declared origin corner: the top row for top-left, and the bottom row for bottom-left. These directions never follow the finished picture, which a build may draw any way its presentation chapter allows. A Delegated view can never change a Fixed answer.",
    "Where a game also has positions, a thing can be between cells and not only on a cell. Zero is the same place for cells and for positions. Where a cell-ownership option makes the cell at zero a different width, that option says so. Two neighboring cells share a line, and cell-ownership says which cell the line belongs to. Every conversion below divides by the cell size and, where the grid counts from 1, adds 1. Each cell-ownership option that uses positions states how position zero and shared lines are treated.",
    "This contract does not cover these related decisions: the grid's edge, two things in one cell, corner-cutting (a diagonal step past the corner of a blocked cell), pathfinding, a third axis, cells that are not squares, and whether a pass over the whole grid reads the changes that the same pass has already made."
  ],
  "questions": {
    "origin-and-axes": {
      "asks": "Where is this grid's first cell, and which way do its row and column numbers grow?",
      "rationale": "Every later rule needs one shared reading of row and column numbers. This contract supports only columns that grow to the right. State a grid that grows to the left in your own prose.",
      "options": {
        "top-left": {
          "meaning": "The first cell is the top-left corner. Column numbers grow right, and row numbers grow down."
        },
        "bottom-left": {
          "meaning": "The first cell is the bottom-left corner. Column numbers grow right, and row numbers grow up."
        },
        "unbounded-right-and-down": {
          "meaning": "There is no first cell or corner. The grid continues through negative and positive numbers. Columns grow right, and rows grow down from the cell your game calls zero."
        },
        "unbounded-right-and-up": {
          "meaning": "There is no first cell or corner. The grid continues through negative and positive numbers. Columns grow right, and rows grow up from the cell your game calls zero."
        }
      }
    },
    "coordinate-order": {
      "asks": "When you write a cell with two numbers, does the row or column come first?",
      "rationale": "Swapping the two numbers turns rows into columns. A grid with the same number of rows and columns can hide that mistake, so the order must be clear.",
      "options": {
        "column-first": {
          "meaning": "The column comes first. The pair (3, 5) means column 3, row 5."
        },
        "row-first": {
          "meaning": "The row comes first. The pair (3, 5) means row 3, column 5."
        },
        "not-applicable": {
          "meaning": "The game never names a cell with a pair of numbers. It uses a layout, cell contents, or another name instead."
        }
      }
    },
    "counting-starts-at": {
      "asks": "Do the first row and column use zero or one?",
      "rationale": "Starting at zero or one changes every written cell address. Naming the start prevents a build in which every address is one cell away from the design.",
      "when": {
        "flag": {
          "origin-and-axes": [
            "top-left",
            "bottom-left"
          ]
        }
      },
      "options": {
        "zero": {
          "meaning": "The first row and column are numbered zero. A ten-cell row runs from zero through nine."
        },
        "one": {
          "meaning": "The first row and column are numbered one. A ten-cell row runs from one through ten."
        }
      }
    },
    "cell-ownership": {
      "asks": "A point lies exactly on the line between two cells. Which cell owns it?",
      "rationale": "A boundary point needs one owner. Different rounding rules can place the same point in different cells, especially beside zero.",
      "options": {
        "next-cell-along": {
          "meaning": "The cell with the larger number owns the line. The line where cell five ends and cell six begins belongs to cell six, on either side of zero.",
          "semantics": "Divide the position by cell-size and round down, then add one when counting-starts-at is one. A boundary position belongs to the cell with the larger coordinate."
        },
        "truncate-toward-zero": {
          "meaning": "The cell farther from zero owns the line. The zero cell reaches one cell-size to each side, so it is twice as wide as the others. The name of this answer describes the calculation: the fraction is cut off, which moves the number toward zero.",
          "semantics": "Divide the position by cell-size and truncate toward zero, then add one when counting-starts-at is one. Coordinate zero spans one cell-size on each side."
        },
        "cell-centers-are-whole-numbers": {
          "meaning": "Whole numbers mark cell centers. A point halfway between two centers belongs to the cell with the larger number.",
          "semantics": "Cell coordinates name centers. Divide the position by cell-size and round to the nearest whole coordinate, taking an exact half toward the larger coordinate, then add one when counting-starts-at is one."
        },
        "not-applicable": {
          "meaning": "Your rules only use whole cells, never positions between them. No boundary choice is needed."
        }
      }
    },
    "distance-metric": {
      "asks": "When your rules say nearest or within some distance, how do they measure between cells?",
      "rationale": "Games often use several distance rules. This answer only controls what your written rules mean by nearest or within a distance.",
      "options": {
        "no-diagonals": {
          "meaning": "Add the steps across and down the grid (Manhattan). A cell two across and one up is three steps away."
        },
        "diagonals-count-the-same": {
          "meaning": "Count the larger of the across and down steps (Chebyshev). A cell two across and one up is two steps away."
        },
        "octile": {
          "meaning": "Straight steps cost one, and diagonal steps cost the square root of two (octile). The distance is the cheapest mix of those steps. Your game's comparison rule decides when two distances count as equal.",
          "semantics": "For absolute coordinate differences dx and dy, multiply the smaller difference by the square root of two minus one (about 0.414), then add the result to the larger difference. Equal means equal at whatever precision this game compares its distances with. For straight-line and octile distance, the adoption must state that comparison rule in the distance test's verification scope."
        },
        "straight-line": {
          "meaning": "Measure a straight line between the cell centers (Euclidean). Use position units when positions exist; otherwise use cells. Your game's comparison rule decides when two distances count as equal.",
          "semantics": "Equal means equal at whatever precision this game compares its distances with. For straight-line and octile distance, the adoption must state that comparison rule in the distance test's verification scope."
        },
        "not-applicable": {
          "meaning": "No rule measures distance between cells. Rules may still use neighbors, named shapes, or links."
        }
      }
    },
    "adjacency-for-movement": {
      "asks": "From one cell, which other cells can a thing reach in one step?",
      "rationale": "Movement neighbors do not follow automatically from distance or effect range. A game can use different cells for each.",
      "options": {
        "four-neighbors": {
          "meaning": "Only the four cells sharing an edge are one step away. A diagonal cell cannot be reached in one step."
        },
        "eight-neighbors": {
          "meaning": "All eight surrounding cells are one step away. A thing may move across an edge or diagonally across a corner."
        },
        "not-applicable": {
          "meaning": "Nothing moves one cell at a time. Things are placed directly or move freely while the grid only reads their final cell."
        }
      }
    },
    "adjacency-for-effects": {
      "asks": "When a rule says two cells are next to each other, do corners count?",
      "rationale": "Movement and effects can count neighbors differently. This answer keeps words such as next to from changing meaning between rules.",
      "options": {
        "four-neighbors": {
          "meaning": "Only cells sharing an edge count as neighbors. Two cells touching only at a corner are not next to each other."
        },
        "eight-neighbors": {
          "meaning": "All eight surrounding cells count as neighbors. Cells touching only at a corner are still next to each other."
        },
        "not-applicable": {
          "meaning": "No rule uses next to by itself. Each rule names the cells it means, or no rule asks whether cells are neighbors."
        }
      }
    },
    "enumeration-order": {
      "asks": "In what order does an authored layout list its cells?",
      "rationale": "Drawing, updates, and save files may use different orders. This answer covers only layouts designers write and read.",
      "options": {
        "rows-then-columns": {
          "meaning": "List every cell in one row before starting the next row. Start with the smallest row and column numbers. A text map with one line per row already uses this order."
        },
        "columns-then-rows": {
          "meaning": "List every cell in one column before starting the next column. Start with the smallest row and column numbers."
        },
        "block-tiled": {
          "meaning": "List cells inside blocks such as chunks, regions, or screens. Your game's prose states block size, block order, and the order inside each block."
        },
        "not-applicable": {
          "meaning": "No authored layout lists the grid's cells. No order is needed for the material designers write and read."
        }
      }
    },
    "tie-break-between-cells": {
      "asks": "A rule rates two cells equally and must pick one. The two cells are the candidates. How does the rule decide?",
      "rationale": "Equal choices are common and rarely written down. A fixed answer stops two builds from choosing different cells.",
      "options": {
        "lower-column-wins": {
          "meaning": "The rule picks the cell with the smaller column number. Between a cell in column 2 and a cell in column 4, the rule picks the cell in column 2. If the column numbers are equal, the rule picks the cell with the smaller row number."
        },
        "lower-row-wins": {
          "meaning": "The rule picks the cell with the smaller row number. Between a cell in row 2 and a cell in row 4, the rule picks the cell in row 2. If the row numbers are equal, the rule picks the cell with the smaller column number."
        },
        "direction-order": {
          "meaning": "The rule tries the grid-fixed direction words in the order that you give them. It picks the tied neighbor in the first direction that has one. Use another answer when the tied cells are not neighbors."
        },
        "arrival-order": {
          "meaning": "The rule picks the candidate that arrived first. Your game names whether arrival means creation, placement, storage, or entering play. Replaying the same run gives the same choice. After a save and a reload, your persistence rules decide. No automatic check covers this answer. A person who reviews the design checks it."
        },
        "named-priority-list": {
          "meaning": "The rule picks the candidate whose kind is listed first in your game's priority order. Cell position never decides."
        },
        "deliberately-arbitrary": {
          "meaning": "The rule may pick either candidate, and players must not depend on which one. Replaying the same run repeats the choice, but loading a save may not."
        },
        "random-from-a-declared-seed": {
          "meaning": "The rule picks one candidate at random from a random stream that your game declares. A random stream is a series of random numbers that starts from a seed. The same run and its replay pick the same candidate. No automatic check covers this answer. A person who reviews the design checks it."
        },
        "player-chooses": {
          "meaning": "The player chooses the candidate. If the game cannot ask, the rule does nothing instead of guessing. No automatic check covers this answer. A person who reviews the design checks it."
        },
        "not-applicable": {
          "meaning": "No rule ever chooses one of two equal candidates. The situation cannot happen, or the rule affects every tied candidate."
        }
      }
    },
    "turn-direction": {
      "asks": "When your rules turn a facing by an amount, which way does the amount go on the grid?",
      "rationale": "Axis direction does not decide turn direction. Naming clockwise or counter-clockwise prevents equivalent formulas from reading as opposite rules.",
      "options": {
        "clockwise": {
          "meaning": "A positive turn goes clockwise on the grid. A rotated view may show it differently, but the grid rule stays the same."
        },
        "counter-clockwise": {
          "meaning": "A positive turn goes counter-clockwise on the grid. A rotated view may show it differently, but the grid rule stays the same."
        },
        "not-applicable": {
          "meaning": "No rule turns a facing by an amount. A piece may still turn at once to face its movement or a target."
        }
      }
    }
  },
  "declares": {
    "values": {
      "cell-size": {
        "description": "The length of one cell in your position units. For center-based cells, measure from one center to the next. Use a positive size when rules read positions. Use zero when they only read whole cells. Changing this number changes which cell holds a position."
      }
    },
    "rows": {
      "directions": {
        "description": "List every direction word your game uses. Each row says whether it follows the grid or a piece. A grid direction also says where it points. An empty list means the game names no directions. If the tie-break answer is direction-order, list every grid-fixed direction in which a tied neighbor can lie. No automatic check covers this. A person who reviews the design checks it.",
        "record": {
          "id": {
            "type": "string",
            "required": true,
            "pattern": "kebab-case",
            "unique": true,
            "description": "The direction word your game uses, such as north, forward, or starboard. Write it in lowercase with hyphens between words."
          },
          "frame": {
            "type": "string",
            "required": true,
            "options": [
              "grid",
              "piece"
            ],
            "description": "Whether the direction follows the grid or a piece. A grid direction always points the same way: north stays north. A piece direction changes when that piece turns: forward, left, and behind turn with it."
          },
          "points": {
            "type": "string",
            "when": {
              "row": {
                "frame": [
                  "grid"
                ]
              }
            },
            "options": [
              "up",
              "down",
              "left",
              "right",
              "up-left",
              "up-right",
              "down-left",
              "down-right"
            ],
            "description": "Where this grid-fixed direction points on the grid. Omit it for a direction that follows a piece. This does not decide whether movement is allowed that way."
          },
          "order": {
            "type": "integer",
            "when": {
              "flag": {
                "tie-break-between-cells": [
                  "direction-order"
                ]
              },
              "row": {
                "frame": [
                  "grid"
                ]
              }
            },
            "unique": true,
            "description": "The place of this direction in the order in which the tie-break tries the directions. The direction with number one is tried first. Give each grid-fixed direction a different number. Use this field only when the tie-break answer is direction-order."
          }
        }
      }
    }
  },
  "rules": {
    "cell-size-not-negative": "cell-size >= 0"
  },
  "pack": "sha256:6f0b75c6c274b81fc83da206fdab2ed800c8447599764b0b04634acfca585fe9",
  "answers": {
    "origin-and-axes": "bottom-left",
    "coordinate-order": "column-first",
    "counting-starts-at": "one",
    "cell-ownership": "not-applicable",
    "distance-metric": "not-applicable",
    "adjacency-for-movement": "eight-neighbors",
    "adjacency-for-effects": "not-applicable",
    "enumeration-order": "rows-then-columns",
    "tie-break-between-cells": "player-chooses",
    "turn-direction": "not-applicable"
  },
  "values": {
    "cell-size": 0
  },
  "rows": {
    "directions": [
      {
        "id": "forward",
        "frame": "piece"
      }
    ]
  },
  "verification": {
    "one-step-moves": {
      "seeds": [
        "chess-king-center",
        "chess-king-center-b"
      ],
      "scope": "the king's one-cell moves from every central square c3 through f6 on an otherwise empty 8x8 board, before checks and occupied squares remove illegal destinations"
    }
  }
}