Game Gravity

In some games, there is a force that pulls game components in one direction, such as gravity pulling objects towards the ground.

gravity

If you want to add this feature to our component constructor, please add a gravity Attribute, which sets the current gravity. Then add a gravitySpeed Properties that increase every time we update the frame:

Examples

function component(width, height, color, x, y, type) {
  this.type = type;
  this.width = width;
  this.height = height;
  this.x = x;
  this.y = y;
  this.speedX = 0;
  this.speedY = 0;
  this.gravity = 0.05;
  this.gravitySpeed = 0;
  this.update = function() {
    ctx = myGameArea.context;
    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;
  }
}

Try it yourself

Touch Bottom

To prevent the red block from falling forever, we need to stop its fall when it reaches the bottom of the game area:

Examples

  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;
    }
  }

Try it yourself

Accelerate

In the game, when there is a force pulling the block down, you should design a method to force the component to accelerate.

A function is triggered when someone clicks the button, making the red block fly into the air:

Examples

<script>
function accelerate(n) {
  myGamePiece.gravity = n;
}
</script>
<button onmousedown="accelerate(-0.2)" onmouseup="accelerate(0.1)">Accelerate</button>

Try it yourself

A game

Make a game based on what we have learned so far:

Examples

Try it yourself

Please click the accelerate button to start the game.

How long can you live? Please use the accelerate button to stay in the air.