游戲分數

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計分

有很多在游戲中記錄分數的方法，我們將向您展示如何將分數寫到畫布上。

首先做一個分數組件：

var myGamePiece;
var myObstacles = [];
var myScore;
function startGame() {
  myGamePiece = new component(30, 30, "red", 10, 160);
  myScore = new component("30px", "Consolas", "black", 280, 40, "text");
  myGameArea.start();
}

在畫布元素上寫入文本的語法與繪制矩形不同。因此，我們必須使用一個額外的參數調用組件構造函數，告訴構造函數該組件的類型為 "text"。

在組件構造函數中，我們測試組件是否為 "text" 類型，并使用 fillText 方法而不是 fillRect 方法：

function component(width, height, color, x, y, type) {
  this.type = type;
  this.width = width;
  this.height = height;
  this.speedX = 0;
  this.speedY = 0;
  this.x = x;
  this.y = y;
  this.update = function() {
    ctx = myGameArea.context;
    if (this.type == "text") {
      ctx.font = this.width + " " + this.height;
      ctx.fillStyle = color;
      ctx.fillText(this.text, this.x, this.y);
    } else {
      ctx.fillStyle = color;
      ctx.fillRect(this.x, this.y, this.width, this.height);
    }
  }
...
}

最后，我們在 updateGameArea 函數中添加一些代碼，將分數寫入畫布。我們使用 frameNo 屬性來計算分數：

function updateGameArea() {
  var x, height, gap, minHeight, maxHeight, minGap, maxGap;
  for (i = 0; i < myObstacles.length; i += 1) {
    if (myGamePiece.crashWith(myObstacles[i])) {
      myGameArea.stop();
      return;
    }
  }
  myGameArea.clear();
  myGameArea.frameNo += 1;
  if (myGameArea.frameNo == 1 || everyinterval(150)) {
    x = myGameArea.canvas.width;
    minHeight = 20;
    maxHeight = 200;
    height = Math.floor(Math.random()*(maxHeight-minHeight+1)+minHeight);
    minGap = 50;
    maxGap = 200;
    gap = Math.floor(Math.random()*(maxGap-minGap+1)+minGap);
    myObstacles.push(new component(10, height, "green", x, 0));
    myObstacles.push(new component(10, x - height - gap, "green", x, height + gap));
  }
  for (i = 0; i < myObstacles.length; i += 1) {
    myObstacles[i].speedX = -1;
    myObstacles[i].newPos();
    myObstacles[i].update();
  }
  myScore.text = "SCORE: " + myGameArea.frameNo;
  myScore.update();
  myGamePiece.newPos();
  myGamePiece.update();
}

親自試一試