<h1>Simple Responsive Modal</h1>
<button>Click For Modal</button>

<!-- modal -->
<div class="modal-overlay">
  <div class="modal">
    
    <a class="close-modal">
      <svg viewBox="0 0 20 20">
        <path fill="#000000" d="M15.898,4.045c-0.271-0.272-0.713-0.272-0.986,0l-4.71,4.711L5.493,4.045c-0.272-0.272-0.714-0.272-0.986,0s-0.272,0.714,0,0.986l4.709,4.711l-4.71,4.711c-0.272,0.271-0.272,0.713,0,0.986c0.136,0.136,0.314,0.203,0.492,0.203c0.179,0,0.357-0.067,0.493-0.203l4.711-4.711l4.71,4.711c0.137,0.136,0.314,0.203,0.494,0.203c0.178,0,0.355-0.067,0.492-0.203c0.273-0.273,0.273-0.715,0-0.986l-4.711-4.711l4.711-4.711C16.172,4.759,16.172,4.317,15.898,4.045z"></path>
      </svg>
    </a><!-- close modal -->

    <div class="modal-content">
      <h3>Some content here</h3>
    </div><!-- content -->
    
  </div><!-- modal -->
</div><!-- overlay -->
/**
 * Variables
 */
$button-bg: #0D52E9;
$speed: 0.6s;
$delay: ($speed * .5);
$easing: cubic-bezier(.55,0,.1,1);


/**
 * Base styles
 */
body,
html {
  background: #080616;
  font-family: 'Roboto', sans-serif;
  text-align: center;
}

h1, h2, h3, h4, h5, h6 {
  font-weight: normal;
}

h1 {
  font-size: 1.875rem;
  font-weight: 300;
  margin: 60px 0 30px 0;
  color: #fff;
}

button {
  background-color: $button-bg;
  position: relative;
  color: #fff;
  border: none;
  padding: 1.25em 2em;
  font-size: 0.75em;
  letter-spacing: 1px;
  text-transform: uppercase;
  cursor: pointer;
  box-shadow: 0 10px 20px rgba(0,0,0,.1);
  transition: background 0.25s $easing;
  
  &:hover {
    background: darken($button-bg, 3%);
  }
  
  &:focus {
    outline: none;
  }
}


/**
 * Overlay
 * -- only show for tablet and up
 */
@media only screen and (min-width: 40em) {
  
  .modal-overlay {
    display: flex;
    align-items: center;
    justify-content: center;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 5;
    background-color: rgba(#000, 0.6);
    opacity: 0;
    visibility: hidden;
    backface-visibility: hidden;
    transition: opacity $speed $easing, visibility $speed $easing;

    &.active {
      opacity: 1;
      visibility: visible;
    }
  }
} // media query



/**
 * Modal
 */
.modal {
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  margin: 0 auto;
  background-color: #fff;
  width: 600px;
  max-width: 75rem;
  min-height: 20rem;
  padding: 1rem;
  border-radius: 3px;
  opacity: 0;
  overflow-y: auto;
  visibility: hidden;
  box-shadow: 0 2px 10px rgba(#000, 0.1);
  backface-visibility: hidden;
  transform: scale(1.2);
  transition: all $speed $easing;
  
  .close-modal {
    position: absolute;
    cursor: pointer;
    top: 5px;
    right: 15px;
    opacity: 0;
    backface-visibility: hidden;
    transition: opacity $speed $easing, transform $speed $easing;
    transition-delay: $delay;
    
    svg {
      width: 1.75em;
      height: 1.75em;
    }
  } // close modal
  
  .modal-content {
    opacity: 0;
    backface-visibility: hidden;
    transition: opacity $speed $easing;
    transition-delay: $delay;
  } // content
  
  &.active {
    visibility: visible;
    opacity: 1;
    transform: scale(1);
    
    .modal-content {
      opacity: 1;
    }
    
    .close-modal {
      transform: translateY(10px);
      opacity: 1;
    }
  }
}



/**
 * Mobile styling
 */
@media only screen and (max-width: 39.9375em) {
  
  h1 {
    font-size: 1.5rem;
  }
  
  .modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    -webkit-overflow-scrolling: touch;
    border-radius: 0;
    transform: scale(1.1);
    padding: 0 !important;
  }
  
  .close-modal {
    right: 20px !important;
  }
} // media query
View Compiled
var elements = $('.modal-overlay, .modal');

$('button').click(function(){
    elements.addClass('active');
});

$('.close-modal').click(function(){
    elements.removeClass('active');
});
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External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://ajax.googleapis.com/ajax/libs/jquery/3.0.0/jquery.min.js