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function HTMLActuator() {
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  this.tileContainer    = document.querySelector(".tile-container");
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  this.scoreContainer   = document.querySelector(".score-container");
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  this.bestContainer    = document.querySelector(".best-container");
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  this.messageContainer = document.querySelector(".game-message");
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  this.score = 0;
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}
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HTMLActuator.prototype.actuate = function (grid, metadata) {
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  var self = this;
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  window.requestAnimationFrame(function () {
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    self.clearContainer(self.tileContainer);
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    grid.cells.forEach(function (column) {
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      column.forEach(function (cell) {
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        if (cell) {
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          self.addTile(cell);
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        }
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      });
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    });
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    self.updateScore(metadata.score);
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    self.updateBestScore(metadata.bestScore);
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    if (metadata.over) self.message(false); // You lose
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    if (metadata.won) self.message(true); // You win!
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  });
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};
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HTMLActuator.prototype.restart = function () {
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  this.clearMessage();
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};
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HTMLActuator.prototype.clearContainer = function (container) {
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  while (container.firstChild) {
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    container.removeChild(container.firstChild);
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  }
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};
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HTMLActuator.prototype.addTile = function (tile) {
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  var self = this;
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  var element   = document.createElement("div");
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  var position  = tile.previousPosition || { x: tile.x, y: tile.y };
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  positionClass = this.positionClass(position);
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  // We can't use classlist because it somehow glitches when replacing classes
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  var classes = ["tile", "tile-" + tile.value, positionClass];
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  if (tile.value > 1048576)
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  classes = ["tile", "tile-" + 1048576, positionClass];
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  this.applyClasses(element, classes);
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  element.textContent = tile.value;
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  if (tile.previousPosition) {
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    // Make sure that the tile gets rendered in the previous position first
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    window.requestAnimationFrame(function () {
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      classes[2] = self.positionClass({ x: tile.x, y: tile.y });
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      self.applyClasses(element, classes); // Update the position
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    });
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  } else if (tile.mergedFrom) {
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    classes.push("tile-merged");
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    this.applyClasses(element, classes);
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    // Render the tiles that merged
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    tile.mergedFrom.forEach(function (merged) {
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      self.addTile(merged);
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    });
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  } else {
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    classes.push("tile-new");
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    this.applyClasses(element, classes);
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  }
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  // Put the tile on the board
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  this.tileContainer.appendChild(element);
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};
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HTMLActuator.prototype.applyClasses = function (element, classes) {
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  element.setAttribute("class", classes.join(" "));
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};
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HTMLActuator.prototype.normalizePosition = function (position) {
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  return { x: position.x + 1, y: position.y + 1 };
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};
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HTMLActuator.prototype.positionClass = function (position) {
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  position = this.normalizePosition(position);
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  return "tile-position-" + position.x + "-" + position.y;
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};
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HTMLActuator.prototype.updateScore = function (score) {
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  this.clearContainer(this.scoreContainer);
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  var difference = score - this.score;
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  this.score = score;
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  this.scoreContainer.textContent = this.score;
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  if (difference > 0) {
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    var addition = document.createElement("div");
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    addition.classList.add("score-addition");
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    addition.textContent = "+" + difference;
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    this.scoreContainer.appendChild(addition);
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  }
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};
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HTMLActuator.prototype.updateBestScore = function (bestScore) {
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  this.bestContainer.textContent = bestScore;
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};
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HTMLActuator.prototype.message = function (won) {
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  var type    = won ? "game-won" : "game-over";
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  var message = won ? "You win!" : "Game over!";
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  this.messageContainer.classList.add(type);
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  this.messageContainer.getElementsByTagName("p")[0].textContent = message;
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};
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HTMLActuator.prototype.clearMessage = function () {
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  this.messageContainer.classList.remove("game-won", "game-over");
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};
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