工程截图

using System;
using System.Collections;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.Serialization;
using TMPro;
/// <summary>
/// 倒计时-数字缩放效果
/// </summary>
public class CountdownEffect : MonoBehaviour
{
    [SerializeField]
    private TextMeshProUGUI _textMeshPro;
    public int second = 5;
    public float minScale = 3f;
    public float maxScale = 10f;
    public float speed = 10f;
    private bool _active = false;
    private float _frameTime;
    private int _cd = 0;
    private bool _zooming = false;

    [Serializable]
    public class OnCompletedEvent : UnityEvent { }
    [FormerlySerializedAs("OnCompleted")]
    [SerializeField]
    private OnCompletedEvent m_OnCompleted = new OnCompletedEvent();

    private void Start()
    {
        _frameTime = Application.targetFrameRate > 0 ? 1.0f / Application.targetFrameRate : 1.0f / 60.0f;
    }

    void Update()
    {
        if (!_active)
            return;
        if (_zooming)
            return;
        if (_cd <= 0)
            return;
        
        StartCoroutine(ZoomIn());
    }

    IEnumerator ZoomIn()
    {
        _zooming = true;
        yield return null;
        
        var rt = _textMeshPro.rectTransform;
        float scale = minScale;
        float scaleTime = 0;
        while (true)
        {
            scale += _frameTime * speed;
            scale = Mathf.Clamp(scale, minScale, maxScale);
            rt.localScale = new Vector3(scale, scale, scale);
            _textMeshPro.text = _cd.ToString();
            Color color = _textMeshPro.color;
            color.a = Mathf.Lerp(0, 1, scale/maxScale);
            _textMeshPro.color = color;
            scaleTime += _frameTime;
            yield return new WaitForSeconds(_frameTime);
            
            if (Mathf.Approximately(scale, maxScale))
                break;
        }

        float remain = 1.0f - scaleTime;
        if (remain > 0f)
            yield return new WaitForSeconds(remain);
       
        _cd--;
        if (_cd <= 0)
            m_OnCompleted?.Invoke();

        _zooming = false;
    }

    public void Play()
    {
        StopAllCoroutines();
        _cd = second;
        _active = true;
        _zooming = false;
    }

    public void ShowText()
    {
        _textMeshPro.gameObject.SetActive(true);
    }

    public void HideText()
    {
        _textMeshPro.gameObject.SetActive(false);
    }
}

运行效果