コルーチン：Update なしで時間かけて処理する

// With Update: three fields and a branch, and the logic is scattered.
bool flashing;
float flashEnds;

void Update()
{
    if (flashing && Time.time >= flashEnds)
    {
        mat.color = Color.white;
        flashing = false;
    }
}

void Hit()
{
    mat.color = Color.red;
    flashing = true;
    flashEnds = Time.time + 0.1f;
}

// With a coroutine: the whole story reads top to bottom, in one place.
IEnumerator Flash()
{
    mat.color = Color.red;
    yield return new WaitForSeconds(0.1f);
    mat.color = Color.white;
}

void Hit() => StartCoroutine(Flash());

yield return null;                              // one frame
yield return new WaitForSeconds(2f);
yield return new WaitForSecondsRealtime(2f);    // two seconds of wall time
yield return new WaitUntil(() => player.isAlive);
yield return StartCoroutine(Other());           // run Other, wait for it to finish

IEnumerator MoveTo(Vector3 to, float seconds)
{
    Vector3 from = transform.position;
    float t = 0f;

    while (t < 1f)
    {
        t += Time.deltaTime / seconds;

        // SmoothStep instead of a plain Lerp: starts and ends gently.
        transform.position = Vector3.Lerp(from, to, Mathf.SmoothStep(0f, 1f, t));
        yield return null;
    }

    // Land exactly on the target: the loop leaves t slightly over 1.
    transform.position = to;
}