<!-- BEGIN COPY / PASTE -->
    <label class="custom-checkbox">
      <input type="checkbox">
      <span class="checkmark"></span>
    </label>

    <style>
      .custom-checkbox {
        display: inline-block;
        position: relative;
        cursor: pointer;
        user-select: none;
      }

      .custom-checkbox input {
        position: absolute;
        opacity: 0;
        cursor: pointer;
      }

      .checkmark {
        width: 20px;
        height: 20px;
        background-color: #eee;
        border-radius: 4px;
        display: inline-block;
        transition: background-color 0.3s;
      }

      .custom-checkbox input:checked + .checkmark {
        background-color: #2196F3;
      }

      .checkmark:after {
        content: "";
        position: absolute;
        display: none;
      }

      .custom-checkbox input:checked + .checkmark:after {
        display: block;
      }

      .custom-checkbox .checkmark:after {
        left: 7px;
        top: 3px;
        width: 5px;
        height: 10px;
        border: solid white;
        border-width: 0 3px 3px 0;
        transform: rotate(45deg);
      }
    </style>
    <!-- END COPY / PASTE -->