​

function Bird() {

  this.y = height / 2;

  this.x = 64;

​

  this.gravity = 0.6;

  this.lift = -15;

  this.velocity = 0;

​

  this.show = function() {

    fill(255);

    noStroke();

    ellipse(this.x, this.y, 32, 32);

  }

​

  this.up = function() {

    this.velocity += this.lift;

  }

​

  this.update = function() {

    this.velocity += this.gravity;

    this.velocity *= 0.9;

    this.y += this.velocity;

​

    if (this.y > height) {

      this.y = height;

      this.velocity = 0;

    }

​

    if (this.y < 0) {

      this.y = 0;

      this.velocity = 0;

    }

​

  }

​

}

​