<input class="radikalwp-ui-inppill" type="text" placeholder="کد تخفیف را وارد کنید">

.radikalwp-ui-inppill {
  width: 280px;
  padding: 12px 24px;
  font-family: inherit;
  font-size: 14px;
  color: #0f172a;
  background: #f1f5f9;
  border: 2px solid transparent;
  border-radius: 999px;
  outline: none;
  transition: background .25s ease, border-color .25s ease, box-shadow .25s ease;
}
.radikalwp-ui-inppill::placeholder { color: #94a3b8; }
.radikalwp-ui-inppill:focus {
  background: #fff;
  border-color: #a5b4fc;
  box-shadow: 0 6px 18px rgba(99, 102, 241, .15);
}