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diff --git a/life2/simulator/src/simulator.js b/life2/simulator/src/simulator.js
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+/**
+ * Copyright 2024 The Life2 Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * @license
+ */
+
+// import * as L2TF from '@life2/format';
+import * as Life2 from '@life2/game';
+
+const WIDTH = 100;
+const HEIGHT = 100;
+
+class RectangularBoard extends Life2.Board {
+  constructor(width, height) {
+    super();
+    this.width = width;
+    this.height = height;
+    this.grid = new Array(this.width)
+                    .fill(new Array(this.height).fill(Life2.Cell.TEAM_A));
+  }
+
+  getCell(x, y) {
+    if (this.isOutOfBounds(x, y)) {
+      return Life2.Cell.BARRIER;
+    }
+
+    return this.grid[x][y];
+  }
+
+  setCell(x, y, cell) {
+    if (this.isOutOfBounds(x, y)) {
+      return;
+    }
+
+    this.grid[x][y] = cell;
+  }
+
+  getNeighbors(x, y) {
+    return [
+      (x - 1, y - 1), (x, y - 1), (x + 1, y - 1), (x - 1, y), (x + 1, y),
+      (x - 1, y + 1), (x, y + 1), (x + 1, y + 1)
+    ].filter((c) => !this.isOutOfBounds(c[0], c[1]))
+        .map((c) => this.getCell(c[0], c[1]));
+  }
+
+  isOutOfBounds(x, y) {
+    return x < 0 || x >= this.width || y < 0 || y >= this.height ||
+        this.grid[x][y] == Life2.Cell.BARRIER;
+  }
+
+  getGrid() {
+    return this.grid;
+  }
+
+  setGrid(grid) {
+    this.grid = grid;
+  }
+
+  getWidth() {
+    return this.width;
+  }
+
+  getHeight() {
+    return this.height;
+  }
+}
+
+// A cell with less than two neighbors of the same team dies of loneliness.
+const lonelinessRule = new Life2.Rule(
+    'Loneliness',
+    'A cell with less than two neighbors of the same team dies of loneliness.',
+    (cell, neighbors) => {
+      if (cell == Life2.Cell.EMPTY) {
+        return;
+      }
+
+      const team = cell;
+      const teamNeighbors = neighbors.filter((c) => c == team);
+      if (teamNeighbors.length < 2) {
+        return Life2.Cell.EMPTY;
+      }
+    });
+
+// A cell with less neighbors of the same team than the other team becomes the
+// other team, = changes teams.
+const teamChangeRule = new Life2.Rule(
+    'Team Change',
+    'A cell with less neighbors of the same team than the other team becomes the other team.',
+    (cell, neighbors) => {
+      if (cell == Life2.Cell.EMPTY) {
+        return;
+      }
+
+      const team = cell;
+      const otherTeam =
+          team == Life2.Cell.TEAM_A ? Life2.Cell.TEAM_B : Life2.Cell.TEAM_A;
+      const teamNeighbors = neighbors.filter((c) => c == team);
+      const otherTeamNeighbors = neighbors.filter((c) => c == otherTeam);
+      if (teamNeighbors.length < otherTeamNeighbors.length) {
+        return otherTeam;
+      }
+    });
+
+// A cell with more than 3 neighbors of the same team dies of overpopulation.
+const overpopulationRule = new Life2.Rule(
+    'Overpopulation',
+    'A cell with more than 3 neighbors of the same team dies of overpopulation.',
+    (cell, neighbors) => {
+      if (cell == Life2.Cell.EMPTY) {
+        return;
+      }
+
+      const team = cell;
+      const teamNeighbors = neighbors.filter((c) => c == team);
+      if (teamNeighbors.length > 3) {
+        return Life2.Cell.EMPTY;
+      }
+    });
+
+// A dead cell with three or more neighbors of the same team becomes that team.
+const birthRule = new Life2.Rule(
+    'Birth',
+    'A dead cell with three or more neighbors of the same team becomes that team.',
+    (cell, neighbors) => {
+      if (cell != Life2.Cell.EMPTY) {
+        return;
+      }
+
+      const teamNeighbors = neighbors.filter((c) => c == Life2.Cell.TEAM_A);
+      if (teamNeighbors.length >= 3) {
+        return Life2.Cell.TEAM_A;
+      }
+
+      const otherTeamNeighbors =
+          neighbors.filter((c) => c == Life2.Cell.TEAM_B);
+      if (otherTeamNeighbors.length >= 3) {
+        return Life2.Cell.TEAM_B;
+      }
+    });
+
+const rules = [lonelinessRule, teamChangeRule, overpopulationRule, birthRule];
+
+const board = new RectangularBoard(WIDTH, HEIGHT);
+const game = new Life2.World(board, rules);
+
+const generationElement = document.getElementById('generation-stats');
+const populationAElement = document.getElementById('population-a-stats');
+const populationBElement = document.getElementById('population-b-stats');
+const deathsAElement = document.getElementById('deaths-a-stats');
+const deathsBElement = document.getElementById('deaths-b-stats');
+const birthsAElement = document.getElementById('births-a-stats');
+const birthsBElement = document.getElementById('births-b-stats');
+
+const speedElement = document.getElementById('speed');
+
+let ITERATION_COUNT = 0;
+let INTERVAL;
+let SLEEP_TIME = speedElement.value;
+
+function updateDisplay() {
+  const grid = game.board.getGrid();
+  const canvas = document.getElementById('board-canvas');
+  const ctx = canvas.getContext('2d');
+  const cellWidth = canvas.width / grid.length;
+  const cellHeight = canvas.height / grid[0].length;
+
+  for (let x = 0; x < grid.length; x++) {
+    for (let y = 0; y < grid[x].length; y++) {
+      if (grid[x][y] == Life2.Cell.TEAM_A) {
+        ctx.fillStyle = 'blue';
+      } else if (grid[x][y] == Life2.Cell.TEAM_B) {
+        ctx.fillStyle = 'red';
+      } else if (grid[x][y] == Life2.Cell.BARRIER) {
+        ctx.fillStyle = 'black';
+      } else {
+        ctx.fillStyle = 'white';
+      }
+
+      ctx.fillRect(x * cellWidth, y * cellHeight, cellWidth, cellHeight);
+    }
+  }
+}
+
+function updateStats() {
+  grid = game.board.getGrid();
+  generationElement.textContent = ITERATION_COUNT;
+  populationAElement.textContent =
+      grid.flatten().filter((c) => c == Life2.Cell.TEAM_A)
+  populationBElement.textContent =
+      grid.flatten().filter((c) => c == Life2.Cell.TEAM_B);
+  deathsAElement.textContent = 0;
+  deathsBElement.textContent = 0;
+  birthsAElement.textContent = 0;
+  birthsBElement.textContent = 0;
+}
+
+function step() {
+  ITERATION_COUNT++;
+  game.step();
+  updateStats();
+  updateDisplay();
+}
+
+export function Simulator_step() {
+  if (INTERVAL) return;
+  step();
+}
+
+export function Simulator_play() {
+  if (INTERVAL) return;
+  INTERVAL = setInterval(step, SLEEP_TIME);
+}
+
+export function Simulator_pause() {
+  if (!INTERVAL) return;
+  clearInterval(INTERVAL);
+}
+
+export function Simulator_save() {
+  console.log('UNIMPLEMENTED');
+  false;
+}
+
+export function Simulator_load() {
+  console.log('UNIMPLEMENTED');
+  false;
+}