[Unity]子buttonを全部押し続けた場合に何か処理したい..てきな？

ButtonGroup.cs

using UnityEngine;
using UnityEngine.EventSystems;

public class ButtonGroup : MonoBehaviour
{
    
    public GameObject[] buttons;
    
    private int counter = 0;
    
    private void Awake()
    {
        foreach (var b in buttons) {
            var trigger = b.AddComponent<EventTrigger>();
            
            // IPointerDownHandler
            EventTrigger.Entry entryDown = new EventTrigger.Entry();
            entryDown.eventID = EventTriggerType.PointerDown;
            entryDown.callback.AddListener( (eventData) => { OnTouchDown(eventData); } );
            trigger.triggers.Add(entryDown);
            
            // IPointerUpHandler
            EventTrigger.Entry entryUp = new EventTrigger.Entry();
            entryUp.eventID = EventTriggerType.PointerUp;
            entryUp.callback.AddListener( (eventData) => { OnTouchUp(eventData); } );
            trigger.triggers.Add(entryUp);
            
        }
    }
    
    private void Update()
    {
        if (counter == buttons.Length) {
            KeepPressingAll();
        }
    }
    
    public void OnTouchDown(BaseEventData eventData)
    {
        counter++;
    }
    
    public void OnTouchUp(BaseEventData eventData)
    {
        counter--;
    }
    
    private void KeepPressingAll()
    {
        Debug.Log("ぜんぶタップ中！！");
    }
    
}