使用GameObject.CompareTag代替GameObject.tag：GameObject.tag会在内部循环调用对象分配的标签属性并分配额外的内存。

    // When this game object intersects a collider with 'is trigger' checked, 
    // store a reference to that collider in a variable named 'other'..
    void OnTriggerEnter(Collider other) 
    {
        // ..and if the game object we intersect has the tag 'Pick Up' assigned to it..
        if (other.gameObject.CompareTag ("Pick Up"))
        {
            // Make the other game object (the pick up) inactive, to make it disappear
            other.gameObject.SetActive (false);

            // Add one to the score variable 'count'
            count = count + 1;

            // Run the 'SetCountText()' function (see below)
            SetCountText ();
        }
    }