AOS

Plugin docs
Animate on scroll library.

              <a href="#" class="btn btn-purple" data-aos="fade-up" data-aos-duration="1000" data-aos-easing="ease-in-out-cubic">

                  Fade up

              </a>


              <a href="#" class="btn btn-success" data-aos="fade-right" data-aos-duration="1000" data-aos-easing="ease-in-out-cubic" data-aos-delay="300">

                  Fade right

              </a>


              <a href="#" class="btn btn-pistachio" data-aos="fade-left" data-aos-duration="1000" data-aos-easing="ease-in-out-cubic" data-aos-delay="600">

                  Fade left

              </a>