checkBounds: function(){
    var x = this.x + this.dx;
    var y = this.y + this.dy;

    var g_o = new Audio();
    g_o.src = "augame/game_over.mp3"

    if ( x < 0 ){
      this.x = 0;
      this.dx = this.velocity;
    } else if ( x + this.width > game.width ){
      this.x = game.width - this.width;
      this.dx = -this.velocity;
    } else if ( y < 0 ){
      this.y = 0;
      this.dy = this.velocity;
    } else if (y + this.height > game.height ){
      game.over("Game Over!");
      g_o.play();
      }