zig Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>
  var myGamePiece;
  var myObstacles = [];
  var myScore;
  function startGame() {
    myGamePiece = new component(30, 30, "red", 10, 120);
    myGamePiece.gravity = 0.05;
    myScore = new component("30px", "Consolas", "black", 280, 40, "text");
    myGameArea.start();
  }
  var myGameArea = {
    canvas: document.createElement("canvas"),
    start: function () {
      this.canvas.width = 480;
      this.canvas.height = 270;
      this.context = this.canvas.getContext("2d");
      document.body.insertBefore(this.canvas, document.body.childNodes[0]);
      this.frameNo = 0;
      this.interval = setInterval(updateGameArea, 20);
    },
    clear: function () {
      this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
  }
  function component(width, height, color, x, y, type) {
    this.type = type;
    this.score = 0;
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;
    this.x = x;
    this.y = y;
    this.gravity = 0;
    this.gravitySpeed = 0;
    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);
      }
    }
    this.newPos = function () {
      this.gravitySpeed += this.gravity;
      this.x += this.speedX;
      this.y += this.speedY + this.gravitySpeed;
      this.hitBottom();
    }
    this.hitBottom = function () {
      var rockbottom = myGameArea.canvas.height - this.height;
      if (this.y > rockbottom) {
        this.y = rockbottom;
        this.gravitySpeed = 0;
      }
    }
    this.crashWith = function (otherobj) {
      var myleft = this.x;
      var myright = this.x + (this.width);
      var mytop = this.y;
      var mybottom = this.y + (this.height);
      var otherleft = otherobj.x;
      var otherright = otherobj.x + (otherobj.width);
      var othertop = otherobj.y;
      var otherbottom = otherobj.y + (otherobj.height);
      var crash = true;
      if ((mybottom < othertop) || (mytop > otherbottom) || (myright < otherleft) || (myleft > otherright)) {
        crash = false;
      }
      return crash;
    }
  }
  function updateGameArea() {
    var x, height, gap, minHeight, maxHeight, minGap, maxGap;
    for (i = 0; i < myObstacles.length; i += 1) {
      if (myGamePiece.crashWith(myObstacles[i])) {
        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].x += -1;
      myObstacles[i].update();
    }
    myScore.text = "SCORE: " + myGameArea.frameNo;
    myScore.update();
    myGamePiece.newPos();
    myGamePiece.update();
  }
  function everyinterval(n) {
    if ((myGameArea.frameNo / n) % 1 == 0) { return true; }
    return false;
  }
  function accelerate(n) {
    myGamePiece.gravity = n;
  }
</script>
<br>
<button onmousedown="accelerate(-0.2)" onmouseup="accelerate(0.05)">ACCELERATE</button>
<p>Use the ACCELERATE button to stay in the air</p>
<p>How long can you stay alive?</p>
</body>

</html>