CSS code for gallery

<style>
.sl-overlay {
  position: fixed;
  left: 0;
  right: 0;
  top: 0;
  bottom: 0;
  background: #fff;
  display: none;
  z-index: 1035;
}

.sl-wrapper {
  z-index: 1040;
  width: 100%;
  height: 100%;
  left: 0;
  top: 0;
  position: fixed;
}
.sl-wrapper * {
  box-sizing: border-box;
}
.sl-wrapper button {
  border: 0 none;
  background: transparent;
  font-size: 28px;
  padding: 0;
  cursor: pointer;
}
.sl-wrapper button:hover {
  opacity: 0.7;
}
.sl-wrapper .sl-close {
  display: none;
  position: fixed;
  right: 30px;
  top: 30px;
  z-index: 10060;
  margin-top: -14px;
  margin-right: -14px;
  height: 44px;
  width: 44px;
  line-height: 44px;
  font-family: Arial, Baskerville, monospace;
  color: #000;
  font-size: 3rem;
}
.sl-wrapper .sl-counter {
  display: none;
  position: fixed;
  top: 30px;
  left: 30px;
  z-index: 10060;
  color: #000;
  font-size: 1rem;
}
.sl-wrapper .sl-download {
  display: none;
  position: fixed;
  bottom: 5px;
  width: 100%;
  text-align: center;
  z-index: 10060;
  color: #fff;
  font-size: 1rem;
}
.sl-wrapper .sl-download a {
  color: #fff;
}
.sl-wrapper .sl-navigation {
  width: 100%;
  display: none;
}
.sl-wrapper .sl-navigation button {
  position: fixed;
  top: 50%;
  margin-top: -22px;
  height: 44px;
  width: 22px;
  line-height: 44px;
  text-align: center;
  display: block;
  z-index: 10060;
  font-family: Arial, Baskerville, monospace;
  color: #000;
}
.sl-wrapper .sl-navigation button.sl-next {
  right: 5px;
  font-size: 2rem;
}
.sl-wrapper .sl-navigation button.sl-prev {
  left: 5px;
  font-size: 2rem;
}
@media (min-width: 35.5em) {
  .sl-wrapper .sl-navigation button {
    width: 44px;
  }
  .sl-wrapper .sl-navigation button.sl-next {
    right: 10px;
    font-size: 3rem;
  }
  .sl-wrapper .sl-navigation button.sl-prev {
    left: 10px;
    font-size: 3rem;
  }
}
@media (min-width: 50em) {
  .sl-wrapper .sl-navigation button {
    width: 44px;
  }
  .sl-wrapper .sl-navigation button.sl-next {
    right: 20px;
    font-size: 3rem;
  }
  .sl-wrapper .sl-navigation button.sl-prev {
    left: 20px;
    font-size: 3rem;
  }
}
.sl-wrapper.sl-dir-rtl .sl-navigation {
  direction: ltr;
}
.sl-wrapper .sl-image {
  position: fixed;
  -ms-touch-action: none;
  touch-action: none;
  z-index: 10000;
}
.sl-wrapper .sl-image img {
  margin: 0;
  padding: 0;
  display: block;
  border: 0 none;
  width: 100%;
  height: auto;
}
@media (min-width: 35.5em) {
  .sl-wrapper .sl-image img {
    border: 0 none;
  }
}
@media (min-width: 50em) {
  .sl-wrapper .sl-image img {
    border: 0 none;
  }
}
.sl-wrapper .sl-image iframe {
  background: #000;
  border: 0 none;
}
@media (min-width: 35.5em) {
  .sl-wrapper .sl-image iframe {
    border: 0 none;
  }
}
@media (min-width: 50em) {
  .sl-wrapper .sl-image iframe {
    border: 0 none;
  }
}
.sl-wrapper .sl-image .sl-caption {
  display: none;
  padding: 10px;
  color: #fff;
  background: rgba(0, 0, 0, 0.8);
  font-size: 1rem;
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
}
.sl-wrapper .sl-image .sl-caption.pos-top {
  bottom: auto;
  top: 0;
}
.sl-wrapper .sl-image .sl-caption.pos-outside {
  bottom: auto;
}

.sl-spinner {
  display: none;
  border: 5px solid #333;
  border-radius: 40px;
  height: 40px;
  left: 50%;
  margin: -20px 0 0 -20px;
  opacity: 0;
  position: fixed;
  top: 50%;
  width: 40px;
  z-index: 1007;
  -webkit-animation: pulsate 1s ease-out infinite;
  -moz-animation: pulsate 1s ease-out infinite;
  -ms-animation: pulsate 1s ease-out infinite;
  -o-animation: pulsate 1s ease-out infinite;
  animation: pulsate 1s ease-out infinite;
}

.sl-scrollbar-measure {
  position: absolute;
  top: -9999px;
  width: 50px;
  height: 50px;
  overflow: scroll;
}

.sl-transition {
  transition: -moz-transform ease 200ms;
  transition: -ms-transform ease 200ms;
  transition: -o-transform ease 200ms;
  transition: -webkit-transform ease 200ms;
  transition: transform ease 200ms;
}

@-webkit-keyframes pulsate {
  0% {
    transform: scale(0.1);
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  100% {
    transform: scale(1.2);
    opacity: 0;
  }
}
@keyframes pulsate {
  0% {
    transform: scale(0.1);
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  100% {
    transform: scale(1.2);
    opacity: 0;
  }
}
@-moz-keyframes pulsate {
  0% {
    transform: scale(0.1);
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  100% {
    transform: scale(1.2);
    opacity: 0;
  }
}
@-o-keyframes pulsate {
  0% {
    transform: scale(0.1);
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  100% {
    transform: scale(1.2);
    opacity: 0;
  }
}
@-ms-keyframes pulsate {
  0% {
    transform: scale(0.1);
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  100% {
    transform: scale(1.2);
    opacity: 0;
  }
}
.gallery a img {
            float: left;
            width: 25%;
            height: auto;
            border: 2px solid #fff;
            -webkit-transition: -webkit-transform .15s ease;
            -moz-transition: -moz-transform .15s ease;
            -o-transition: -o-transform .15s ease;
            -ms-transition: -ms-transform .15s ease;
            transition: transform .15s ease;
            position: relative;
        }
</style>