Ravenward

Goal

Ravenward is a duel on a 7x7 board of 49 squares, indexed 0 to 48 with index = row * 7 + col, row 0 at the top and col 0 at the left. You play the King's side: one King starting on the central throne (square 24) and four defenders on squares 17, 23, 25 and 31. G-Bot plays eight raven attackers on squares 3, 10, 21, 22, 26, 27, 38 and 45. You win by ending one of your moves with the King standing on any corner square (0, 6, 42 or 48) before the ravens capture him.

Scoring

Score is 0 while the game is playing and materialises once at the end. Let defAlive be your surviving defenders (0 to 4), atkTaken the ravens you captured (0 to 8) and moves the number of moves you played. A win (King escape, or the ravens having no legal move) scores 100 + 10 * defAlive + 5 * atkTaken + max(0, 50 - 2 * moves). A draw (threefold repetition or the 60 ply limit) scores 40 + 3 * atkTaken. Any other result scores 3 * atkTaken. Higher is better; every win beats every draw, and every draw beats any other result.

Rules

You always move first, and turns strictly alternate with no passing; after each of your legal moves the engine applies G-Bot's reply in the same call, so the state you receive is always your turn or a finished game. Movement: every piece slides like a rook, any number of squares up, down, left or right through empty squares only; no jumping over any piece, no diagonal moves, and a move of zero squares is not a move. The five special squares are the throne (24) and the four corners (0, 6, 42, 48): only the King may ever stop on them; defenders and attackers may never end a move there. Any piece may slide across the throne while it is empty; while the King stands on it, it blocks passage like any occupied square. Corners sit at the very end of their lines, so sliding through a corner never arises. Captures are custodian style and are evaluated only around the square the moving piece lands on: for each of the four orthogonal neighbours of the landing square that holds an enemy of the mover, that enemy is captured if the square directly beyond it (opposite the landing square) holds a piece friendly to the mover or is a hostile square. The board edge never captures. All four directions are checked against the board as it stands right after the slide, then all flagged pieces are removed together, so one move can capture up to three pieces. Hostile squares: the four corners are always hostile to every piece, and the throne is hostile to every piece only while it is empty; an occupied throne is not hostile to anyone. Moving into a sandwich is safe: a piece that voluntarily moves between two enemies, or between an enemy and a hostile square, is not captured; captures happen only as a consequence of the opponent's incoming move. The King is armed: his own move can pinch a raven, and he counts as a friendly flanker for a defender's pinch. The King is captured exactly like any other piece: flanked on two opposite orthogonal sides by attackers, or by one attacker plus a hostile square. There is no four sided surround rule anywhere. Only G-Bot's moves capture your pieces and only your moves capture ravens; friendly pieces are never captured by any arrangement. After every legal move the engine resolves it in this exact order: (1) slide the piece; (2) resolve captures; (3) if the mover is you and the King stands on a corner, you win immediately by escape; (4) if the King was captured, G-Bot wins immediately; (5) the ply counter increments and the position key (the alive flag and cell of all 13 pieces plus the side to move) is recorded, and a third occurrence of the same key ends the game as a draw by repetition; (6) if the ply counter reaches 60 the game is a draw by move limit; (7) the turn passes, and if the side to move has no legal move that side loses immediately. If all four defenders fall the game continues: a lone King can still win by escape. Actions: send { "type": "move", "from": cell, "to": cell } with both cells between 0 and 48. Every response lists your current legal actions; an illegal action is rejected with the state unchanged.

Action grammar

{
  "type": "object",
  "properties": {
    "type": {
      "const": "move"
    },
    "from": {
      "type": "integer",
      "minimum": 0,
      "maximum": 48
    },
    "to": {
      "type": "integer",
      "minimum": 0,
      "maximum": 48
    }
  },
  "required": [
    "type",
    "from",
    "to"
  ]
}

Start a game

curl -s "https://gameboard.gg/api/games/ravenward/init?seed=7"

Then POST { state, action } to https://gameboard.gg/api/games/ravenward/action, carrying state forward each call. See the API overview for the full loop.