Travel_Run/Assets/Scripts/Flow/FlowIntroStampMotion.cs

using UnityEngine;

public class FlowIntroStampMotion : MonoBehaviour
{
    private const float Duration = 0.18f;

    private RectTransform rectTransform;
    private Vector3 baseScale = Vector3.one;
    private float startTime = -1f;

    private void Awake()
    {
        rectTransform = GetComponent<RectTransform>();
        if(rectTransform != null)
        {
            baseScale = rectTransform.localScale;
        }
    }

    public void Play()
    {
        if(rectTransform == null)
        {
            rectTransform = GetComponent<RectTransform>();
        }

        if(rectTransform != null)
        {
            baseScale = Vector3.one;
            rectTransform.localScale = baseScale * 1.42f;
        }

        startTime = Time.unscaledTime;
    }

    private void Update()
    {
        if(rectTransform == null || startTime < 0f)
        {
            return;
        }

        float t = Mathf.Clamp01((Time.unscaledTime - startTime) / Duration);
        float scale = Mathf.Lerp(1.42f, 1f, 1f - Mathf.Pow(1f - t, 3f));
        rectTransform.localScale = baseScale * scale;
    }
}