text: function Bird() {
      this.y = height/2;
      this.x = 64;
  
      this.gravity = 0.3;
      this.lift = -15;
      this.velocity = 0;
  
      this.show = function() {
          fill(225);
          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;
          }
      }
  }