code: function(dist) {
      var dx = Math.cos(this.dir) * dist;
      var dy = Math.sin(this.dir) * dist;
  
      // Move the player if they can walk here.
      this.x += (game.map.check(this.x + dx, this.y) <= 0) ? dx : 0;
      this.y += (game.map.check(this.x, this.y + dy) <= 0) ? dy : 0;
  
      this.steps += dist;
  
      // Update the position of the audio listener.
      Howler.pos(this.x, this.y, -0.5);
    }
docs: Handle walking based on the state of inputs.
  @param  {Number} dist Distance to walk based on time elapsed.