er>
    <button id="BacktoTop">
        <div class="circle1">
          <svg
            id="back-to-top"
            xmlns="http://www.w3.org/2000/svg"
            width="30"
            height="30"
            fill="currentColor"
            class="bi bi-arrow-up-circle-fill"
            viewBox="0 0 16 16"
          >
            <path
              d="M16 8A8 8 0 1 0 0 8a8 8 0 0 0 16 0m-7.5 3.5a.5.5 0 0 1-1 0V5.707L5.354 7.854a.5.5 0 1 1-.708-.708l3-3a.5.5 0 0 1 .708 0l3 3a.5.5 0 0 1-.708.708L8.5 5.707z