<label class="button success tiny" for="modal-1">Email this user</label>

<input class="modal-state" id="modal-1" type="checkbox" />
    <div class="modal">
      <label class="modal__bg" for="modal-1"></label>
      <div class="modal__inner">
        <label class="modal__close" for="modal-1"></label>
        <h2>Modal Inside Title</h2>
        <p><?php echo do_shortcode('[gravityform id="80" title="false" description="false"]'); ?>
    </p>
      </div>
    </div>

/* [Object] Modal
 * =============================== */
.modal {
  opacity: 0;
  visibility: hidden;
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  text-align: left;
  background: rgba(0,0,0, .9);
  transition: opacity .25s ease;
}

.modal__bg {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  cursor: pointer;
}

.modal-state {
  display: none;
}

.modal-state:checked + .modal {
  opacity: 1;
  visibility: visible;
}

.modal-state:checked + .modal .modal__inner {
  top: 0;
}

.modal__inner {
  transition: top .25s ease;
  position: absolute;
  top: -20%;
  right: 0;
  bottom: 0;
  left: 0;
  width: 50%;
  margin: auto;
  overflow: auto;
  background: #fff;
  border-radius: 5px;
  padding: 1em 2em;
  height: 50%;
}

.modal__close {
  position: absolute;
  right: 1em;
  top: 1em;
  width: 1.1em;
  height: 1.1em;
  cursor: pointer;
}

.modal__close:after,
.modal__close:before {
  content: '';
  position: absolute;
  width: 2px;
  height: 1.5em;
  background: #ccc;
  display: block;
  transform: rotate(45deg);
  left: 50%;
  margin: -3px 0 0 -1px;
  top: 0;
}

.modal__close:hover:after,
.modal__close:hover:before {
  background: #aaa;
}

.modal__close:before {
  transform: rotate(-45deg);
}

@media screen and (max-width: 768px) {

  .modal__inner {
    width: 90%;
    height: 90%;
    box-sizing: border-box;
  }
}