Duskcourt

Goal

A small sandstone court holds a handful of carved animal idols, and there is exactly one verb: capture. Every move takes an idol with another idol; there is no move to an empty square. Clear the court by capturing until one idol stands alone, and the next rung deals a harder court: more idols, then a bigger court, then more decoys, then the two twists (a jackal that can never be taken and must make the last take, and fallen boulders that block the running idols). The tension is that every capture removes a capturer: take the wrong idol first and the one that could have finished the job is gone. When idols remain and no capture exists anywhere, the court is stuck, a life is lost and a fresh court is dealt at the same rung. You have 3 lives and they do not come back. The ladder never ends: it keeps climbing until your lives run out or you stop at a break and keep your score. Play it backwards: find the idol that could make the last take, then the one before it, and play the chain forwards.

Scoring

Higher is better, and the score only ever goes up: nothing subtracts, and a run that goes badly simply stops adding. With r the rung of the court being played, every capture pays 10 + 2 * (r - 1), and it is paid by depth once per court: capture number k of an attempt pays only if k is deeper than state.paidDepth, so replaying captures after a reset pays nothing until the replay goes deeper than any earlier attempt did. Clearing the court pays 40 * r. A streak award pays 10 * r * min(streak, 5) on the clear, where streak counts consecutive clears since the last lost life, this clear included; a reset does not break the streak and a stuck court does. A clean clear award pays 20 * r for clearing without having used reset on that court. A stuck court, a reset, a lost life and endRun pay and cost exactly nothing: stopping keeps the current score. state.lastAward carries the last clear's four awards and their total.

Rules

THE COURT. A square court of size x size squares, size being four, five or six depending on the rung, addressed by one index i = row * size + col. Row 0 is the bottom rank and forward means toward row size - 1 at the top. state.board holds size * size cells: null for an empty square, "#" for a boulder, or one letter for an idol. state.dealt is the court exactly as it was dealt, and it is public. Every idol is yours; there are no sides and every idol can take every other idol, subject to the jackal rule below. THE IDOLS AND THEIR REACH. K, the jackal: takes on any of the eight squares touching its own. Q, the scorpion: runs any distance along any of the eight lines through its square, the four straight lines and the four diagonals. R, the cobra: runs any distance along the four straight lines. B, the vulture: runs any distance along the four diagonals. N, the camel: jumps to any of the eight squares that lie two along one axis and one along the other, ignoring anything in between. P, the beetle: takes on exactly the two squares diagonally forward, (row + 1, col - 1) and (row + 1, col + 1), so a beetle on the top row has no takes at all, though it can still be taken. A running idol (Q, R or B) stops at the first occupied square along a line and takes it only if it is an idol; a boulder blocks the line and nothing runs past it. THE ONE MOVE. Every move is a capture: { "type": "capture", "from": i, "to": j } moves the idol at from onto the idol at to and removes the taken idol. There is no move to an empty square, no pass and no turn to end. getLegalActions lists every legal capture in index order, so you never have to work the reach out yourself. CLEAR AND STUCK. After each capture the engine counts the idols left. Exactly one left: the court is cleared, the awards are paid, and state.phase becomes break with state.lastResult clear. Two or more left with no legal capture anywhere: the court is stuck, one life is lost, the streak returns to zero, and phase becomes break with lastResult stuck, or done if that was the last life. A run has 3 lives and they do not regenerate. Both outcomes resolve on the capture itself; there is no separate check and no way to sit on a stuck court. THE BREAK. Exactly two actions. { "type": "next" } deals the next court: one rung higher after a clear, and at the same rung after a stuck court (a fresh draw from the seeded stream, never the same court again). { "type": "endRun" } ends the run where it stands and keeps the current score, with no bonus and no cost; it is offered at every break, cleared or stuck, so a long run can be closed at a natural beat. The rung is never lost. THE JACKAL MUST STAND LAST. On a court with state.kingSurvives true there is exactly one K, it can never be taken, and a capture whose to is the K is refused. The K takes normally, so the only way to clear such a court is for the K to make the final take. BOULDERS. state.boulders squares hold "#" for the whole court. They are never taken, never moved and never entered; they block Q, R and B, and N jumps over them. RESET. { "type": "reset" } restores the court to state.dealt. It is legal only while phase is playing, only after at least one capture on this court, and only once per court (state.resetUsed says whether it is spent). It forfeits the clean clear award for this court, keeps the streak and costs no life. It is not offered on a stuck court, because a stuck court has already left play: a reset has to be taken before the capture that strands you. PHASES AND REFUSALS. phase is playing, break or done. A run opens at rung 1 already playing, so the first action is a capture. Any action out of phase, any capture that is not a legal take, a reset the rule refuses and anything at all after done is refused with the legal list, costs nothing and changes nothing, not even the random cursor. DETERMINISM. Every court is dealt from a seeded stream carried in state, advanced only when a court is dealt; a capture and a reset draw nothing, so the same seed and the same action list replay the same run byte for byte. Every dealt court can be cleared: there is always a way through, and the run is never dealt a court that is already stuck.

Action grammar

{
  "type": "object",
  "oneOf": [
    {
      "type": "object",
      "properties": {
        "type": {
          "const": "capture",
          "description": "Take the idol at to with the idol at from. Legal only while phase is playing, only when to is within the reach of the idol at from, and never onto the jackal on a court where the jackal must stand last."
        },
        "from": {
          "type": "integer",
          "minimum": 0,
          "maximum": 35,
          "description": "The square the taking idol stands on, an index from 0 to 35 where index = row * size + col and row 0 is the bottom rank. Must hold an idol on this court."
        },
        "to": {
          "type": "integer",
          "minimum": 0,
          "maximum": 35,
          "description": "The square of the idol to take, an index from 0 to 35. Must hold an idol within the reach of the idol at from; never an empty square or a boulder."
        }
      },
      "required": [
        "type",
        "from",
        "to"
      ],
      "additionalProperties": false
    },
    {
      "type": "object",
      "properties": {
        "type": {
          "const": "reset",
          "description": "Restore the court to state.dealt. Legal only while playing, only after at least one capture on this court, and only once per court. It forfeits the clean clear award, keeps the streak and costs no life."
        }
      },
      "required": [
        "type"
      ],
      "additionalProperties": false
    },
    {
      "type": "object",
      "properties": {
        "type": {
          "const": "next",
          "description": "Deal the next court. Legal only while phase is break: one rung higher after a clear, the same rung after a stuck court."
        }
      },
      "required": [
        "type"
      ],
      "additionalProperties": false
    },
    {
      "type": "object",
      "properties": {
        "type": {
          "const": "endRun",
          "description": "Stop at the break and keep the current score. Legal only while phase is break. It pays no bonus, costs nothing and moves no random cursor."
        }
      },
      "required": [
        "type"
      ],
      "additionalProperties": false
    }
  ]
}

Start a game

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

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