enclose/index.html at master · irondavy/enclose · GitHub

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<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Enclose Horse</title>
    <style>
      * {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
        image-rendering: pixelated;
      }
      body {
        display: flex;
        flex-direction: column;
        justify-content: center;
        align-items: center;
        min-height: 100vh;
        background: #fff;
        font-family: "Chicago", "Geneva", "Monaco", monospace;
      }
      #status {
        color: #000;
        font-size: 0.9rem;
        margin-top: 0.75rem;
        display: flex;
        align-items: center;
        gap: 1rem;
      }
      #status label {
        font-size: 0.75rem;
        color: #000;
        cursor: pointer;
        display: flex;
        align-items: center;
        gap: 0.3rem;
      }
      canvas {
        border: 2px solid #000;
        background: #fff;
      }
    </style>
  </head>
  <body>
    <canvas id="game" width="640" height="640"></canvas>
    <div id="status">
      <span id="counts"></span
      ><label
        ><input type="checkbox" id="showProtected" /> show protected</label
      >
    </div>
    <script>
      const canvas = document.getElementById("game");
      const ctx = canvas.getContext("2d");

      const GRID = 10;
      const CELL = canvas.width / GRID;

      const MAX_STONES = 10;
      const WATER_TARGET = 20;
      const edgeTargets = [
        [0, -1],
        [0, 1],
        [-1, 0],
        [1, 0],
      ];

      function minCutToEdge(hc, hr, waterSet) {
        const N = GRID * GRID;
        const SRC = N * 2;
        const SINK = SRC + 1;
        const NODES = SINK + 1;
        const cap = Array.from({ length: NODES }, () => new Int32Array(NODES));
        const adj = Array.from({ length: NODES }, () => []);

        function addEdge(u, v, c) {
          cap[u][v] += c;
          adj[u].push(v);
          adj[v].push(u);
        }

        const id = (c, r) => r * GRID + c;
        const IN = (c, r) => id(c, r) * 2;
        const OUT = (c, r) => id(c, r) * 2 + 1;

        for (let r = 0; r < GRID; r++) {
          for (let c = 0; c < GRID; c++) {
            if (waterSet.has(`${c},${r}`)) continue;
            if (c === hc && r === hr) {
              addEdge(IN(c, r), OUT(c, r), 1000);
            } else {
              addEdge(IN(c, r), OUT(c, r), 1);
            }
            for (const [dc, dr] of edgeTargets) {
              const nc = c + dc,
                nr = r + dr;
              if (nc < 0 || nr < 0 || nc >= GRID || nr >= GRID) continue;
              if (waterSet.has(`${nc},${nr}`)) continue;
              addEdge(OUT(c, r), IN(nc, nr), 1000);
            }
            if (c === 0 || r === 0 || c === GRID - 1 || r === GRID - 1) {
              addEdge(OUT(c, r), SINK, 1000);
            }
          }
        }
        addEdge(SRC, IN(hc, hr), 1000);

        let totalFlow = 0;
        while (true) {
          const parent = new Int32Array(NODES).fill(-1);
          parent[SRC] = SRC;
          const queue = [SRC];
          let found = false;
          for (let qi = 0; qi < queue.length && !found; qi++) {
            const u = queue[qi];
            for (const v of adj[u]) {
              if (parent[v] === -1 && cap[u][v] > 0) {
                parent[v] = u;
                if (v === SINK) {
                  found = true;
                  break;
                }
                queue.push(v);
              }
            }
          }
          if (!found) break;
          let flow = Infinity;
          for (let v = SINK; v !== SRC; v = parent[v]) {
            flow = Math.min(flow, cap[parent[v]][v]);
          }
          for (let v = SINK; v !== SRC; v = parent[v]) {
            cap[parent[v]][v] -= flow;
            cap[v][parent[v]] += flow;
          }
          totalFlow += flow;
          if (totalFlow > MAX_STONES) return totalFlow;
        }
        return totalFlow;
      }

      function generateMap() {
        const hc = 3 + Math.floor(Math.random() * 4);
        const hr = 3 + Math.floor(Math.random() * 4);

        const prot = new Set();
        prot.add(`${hc},${hr}`);
        for (const [pdc, pdr] of edgeTargets) {
          let c = hc,
            r = hr;
          const sideways = Math.random() < 0.5 ? 1 : -1;
          const atTargetEdge = () =>
            (pdc === -1 && c === 0) ||
            (pdc === 1 && c === GRID - 1) ||
            (pdr === -1 && r === 0) ||
            (pdr === 1 && r === GRID - 1);
          while (!atTargetEdge()) {
            if (Math.random() < 0.7) {
              c += pdc;
              r += pdr;
            } else {
              if (pdc === 0) c += sideways;
              else r += sideways;
            }
            c = Math.max(0, Math.min(GRID - 1, c));
            r = Math.max(0, Math.min(GRID - 1, r));
            prot.add(`${c},${r}`);
          }
        }

        const w = new Set();
        const spiralTiles = [];
        for (let ring = 0; ring < Math.ceil(GRID / 2); ring++) {
          const lo = ring,
            hi = GRID - 1 - ring;
          for (let c = lo; c <= hi; c++) spiralTiles.push([c, lo]);
          for (let r = lo + 1; r <= hi; r++) spiralTiles.push([hi, r]);
          for (let c = hi - 1; c >= lo; c--) spiralTiles.push([c, hi]);
          for (let r = hi - 1; r > lo; r--) spiralTiles.push([lo, r]);
        }
        let i = 0;
        while (i < spiralTiles.length) {
          const [c, r] = spiralTiles[i];
          const key = `${c},${r}`;
          if (c !== hc || r !== hr) {
            if (!prot.has(key)) {
              w.add(key);
            }
          }
          i += 1 + Math.floor(Math.random() * 3) + 1;
        }

        return { hc, hr, prot, w };
      }

      let attempts = 0;
      let horseCol, horseRow, protected_, water;
      while (true) {
        attempts++;
        const map = generateMap();
        const cut = minCutToEdge(map.hc, map.hr, map.w);
        if (cut <= MAX_STONES - 3) {
          horseCol = map.hc;
          horseRow = map.hr;
          protected_ = map.prot;
          water = map.w;
          break;
        }
      }

      const stones = new Set();

      function drawStoneFill(col, row) {
        const x = col * CELL;
        const y = row * CELL;
        ctx.fillStyle = "#000";
        ctx.fillRect(x, y, CELL, CELL);
        ctx.fillStyle = "#fff";
        for (let py = 0; py < CELL; py += 4) {
          for (let px = 0; px < CELL; px += 4) {
            if ((px / 4 + py / 4) % 2 === 0) {
              ctx.fillRect(x + px, y + py, 2, 2);
            }
          }
        }
      }

      function drawHorse(col, row) {
        const x = col * CELL;
        const y = row * CELL;
        ctx.font = `${CELL * 0.8}px serif`;
        ctx.textAlign = "center";
        ctx.textBaseline = "middle";
        ctx.fillText("♞", x + CELL / 2, y + CELL / 2 + 2);
      }

      function isEdge(c, r) {
        return c === 0 || r === 0 || c === GRID - 1 || r === GRID - 1;
      }

      function isBlocked(c, r) {
        return water.has(`${c},${r}`) || stones.has(`${c},${r}`);
      }

      function findPathToEdge() {
        const dirs = [
          [0, -1],
          [0, 1],
          [-1, 0],
          [1, 0],
        ];
        const visited = new Set();
        const prev = new Map();
        const queue = [[horseCol, horseRow]];
        visited.add(`${horseCol},${horseRow}`);

        while (queue.length > 0) {
          const [cx, cy] = queue.shift();
          if (isEdge(cx, cy)) {
            const path = [];
            let key = `${cx},${cy}`;
            while (key) {
              const [px, py] = key.split(",").map(Number);
              path.unshift({ c: px, r: py });
              key = prev.get(key);
            }
            return { path, enclosed: null };
          }
          for (const [dx, dy] of dirs) {
            const nx = cx + dx,
              ny = cy + dy;
            const nk = `${nx},${ny}`;
            if (nx < 0 || ny < 0 || nx >= GRID || ny >= GRID) continue;
            if (visited.has(nk) || isBlocked(nx, ny)) continue;
            visited.add(nk);
            prev.set(nk, `${cx},${cy}`);
            queue.push([nx, ny]);
          }
        }
        return { path: null, enclosed: visited };
      }

      let hovering = false;
      let escapePath = null;
      let enclosedTiles = null;

      function updateStatus() {
        const el = document.getElementById("counts");
        const enclosed = enclosedTiles ? enclosedTiles.size : 0;
        el.textContent = `Stones: ${stones.size}/${MAX_STONES} · Enclosed: ${enclosed} · Map attempts: ${attempts}`;
      }

      function draw() {
        ctx.clearRect(0, 0, canvas.width, canvas.height);

        ctx.strokeStyle = "#000";
        ctx.lineWidth = 1;
        for (let r = 0; r < GRID; r++) {
          for (let c = 0; c < GRID; c++) {
            const key = `${c},${r}`;
            if (water.has(key)) {
              ctx.fillStyle = "#000";
              ctx.fillRect(c * CELL, r * CELL, CELL, CELL);
            } else if (stones.has(key)) {
              drawStoneFill(c, r);
            }
            ctx.strokeRect(c * CELL, r * CELL, CELL, CELL);
          }
        }

        if (document.getElementById("showProtected").checked) {
          for (const key of protected_) {
            const [c, r] = key.split(",").map(Number);
            if (!water.has(key) && !stones.has(key)) {
              ctx.fillStyle = "rgba(0, 0, 0, 0.08)";
              ctx.fillRect(c * CELL, r * CELL, CELL, CELL);
            }
          }
        }

        if (enclosedTiles) {
          ctx.fillStyle = "#000";
          for (const key of enclosedTiles) {
            const [c, r] = key.split(",").map(Number);
            const x = c * CELL,
              y = r * CELL;
            for (let py = 0; py < CELL; py += 4) {
              for (let px = 0; px < CELL; px += 4) {
                if ((px / 4 + py / 4) % 4 === 0) {
                  ctx.fillRect(x + px, y + py, 2, 2);
                }
              }
            }
          }
        } else if (hovering && escapePath) {
          ctx.fillStyle = "rgba(0, 0, 0, 0.12)";
          for (const { c, r } of escapePath) {
            if (c === horseCol && r === horseRow) continue;
            ctx.fillRect(c * CELL, r * CELL, CELL, CELL);
          }
        }

        ctx.fillStyle = "#000";
        drawHorse(horseCol, horseRow);
      }

      canvas.addEventListener("mousemove", (e) => {
        const rect = canvas.getBoundingClientRect();
        const col = Math.floor((e.clientX - rect.left) / CELL);
        const row = Math.floor((e.clientY - rect.top) / CELL);
        const wasHovering = hovering;
        hovering = col === horseCol && row === horseRow;
        if (hovering && !wasHovering && !enclosedTiles) {
          const result = findPathToEdge();
          escapePath = result.path;
        }
        if (hovering !== wasHovering) draw();
      });

      canvas.addEventListener("mouseleave", () => {
        hovering = false;
        escapePath = null;
        draw();
      });

      canvas.addEventListener("click", (e) => {
        const rect = canvas.getBoundingClientRect();
        const col = Math.floor((e.clientX - rect.left) / CELL);
        const row = Math.floor((e.clientY - rect.top) / CELL);
        const key = `${col},${row}`;
        if (col === horseCol && row === horseRow) return;
        if (water.has(key)) return;
        if (stones.has(key)) {
          stones.delete(key);
          enclosedTiles = null;
          updateStatus();
          draw();
          return;
        }
        if (enclosedTiles) return;
        if (stones.size >= MAX_STONES) return;
        stones.add(key);
        const result = findPathToEdge();
        if (result.enclosed) {
          enclosedTiles = result.enclosed;
        }
        updateStatus();
        draw();
      });

      document.getElementById("showProtected").addEventListener("change", draw);

      updateStatus();
      draw();
    </script>
  </body>
</html>