<button class="radikalwp-backtop" type="button" title="بازگشت به بالا">↑<//button>

.radikalwp-backtop {
  position: fixed; bottom: 22px; left: 22px; width: 46px; height: 46px; border: 0; border-radius: 50%;
  background: #4f46e5; color: #fff; font-size: 18px; font-weight: 800; cursor: pointer;
  box-shadow: 0 10px 24px rgba(79,70,229,.4); transition: transform .25s, background .25s;
}
.radikalwp-backtop:hover { transform: translateY(-4px); background: #4338ca; }