<div class="wrapper">
  <a class="button" href="#pop">Click!</a>
</div>

<div id="pop" class="overlay">
  <div class="modal">
    <h2>Hey there!</h2>
    <a class="close" href="#">&times;</a>
    <div class="content">
      So, here we are:<br/>
      I am a pure (S)CSS Modal and work with the <strong>:target</strong> element.<br/><br/>
      You can close me by clicking the x in the upper left corner or the button at the bottom.<br/><br/>
      See you next time:)<br/><br/>
      <a class="button" href="#">Close</a>
    </div>
  </div>
</div>

@mixin border-radius($radius) {
  border-radius: $radius;
  -webkit-border-radius: $radius;
  -moz-border-radius: $radius;
}

html, body {
  height: 100%;
  -webkit-font-smoothing: antialiased;
  -webkit-tap-highlight-color: transparent;
}
body {
  margin: 0;
  background-color: #FAFAFB;
  color: slategrey;
}

a.button {
  text: {
    decoration: none;
    align: center;
    shadow: 0 1px 0 #fff;
  }
  color: steelblue;
  font-weight: 500;
  padding: 8px 15px 8px 15px;
  border: 1px solid rgba(26,53,71,.1);
  @include border-radius(4px);
  transition: .25s;
  background: linear-gradient(white, ghostwhite);
  &:hover {
    border: 1px solid rgba(26,53,71,.2);
    background: white;
  }
}

.wrapper {
  width: 600px;
  height: 100%;
  margin: auto;
  text-align: center;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  align-items: center;
  justify-content: center;
}

.overlay {
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background: rgba(0, 0, 0, 0.7);
  transition: opacity .5s;
  visibility: hidden;
  opacity: 0;
  &:target {
    visibility: visible;
    opacity: 1;
  }
}

.modal {
  width: 400px;
  position: relative;
  margin: auto;
  padding: 1.5rem;
  background: #fff;
  @include border-radius(4px);
  transition: .5s;
  opacity: 0;
  .content {
    margin-top: 1rem;
    a {
      max-width: 60%;
      margin: auto;
      display: block;
    }
  }
}

.overlay:target > .modal {
  transform: translateY(30%) scale(0.9);
  transition-timing-function: cubic-bezier(.8, 0, 0, 1.5);
  opacity: 1;
}

h2 {
  text-align: center;
  margin-top: 2rem;
}

a.close {
  position: absolute;
  top: 15px;
  left: 15px;
  width: 22px;
  height: 22px;
  text: {
    decoration: none;
    align: center;
  }
  font-size: 20px;
  line-height: 21px;
  color: lightslategrey;
  background-color: lightgrey;
  @include border-radius(50%);
  transition: .25s;
  &:hover {
    background-color: tomato;
    color: white;
  }
}