Smooth Accordion In Pure HTML And CSS

Preview:

Description:

A pure HTML/CSS accordion component that uses CSS3 transitions for smooth animations when expanding/collapsing.

How to use it:

The basic html structure for the accordion. In this case, we’re going to use html checkbox and label for the toggles.

<div class="block">
  <div>
    <input type="radio" name="item" id="item-one" checked hidden />
    <label for="item-one">Item 1</label>
    <div>
      <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Debitis praesentium, perspiciatis optio repellat quos maiores cum, tempore veniam ratione delectus quae ex laudantium modi. Quam sequi illo laudantium, harum odio.</p>
    </div>
  </div>
  <div>
    <input type="radio" name="item" id="item-two" hidden />
    <label for="item-two">Item 2</label>
    <div>
      <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Debitis praesentium, perspiciatis optio repellat quos maiores cum, tempore veniam ratione delectus quae ex laudantium modi. Quam sequi illo laudantium, harum odio.</p>
    </div>
  </div>
  <div>
    <input type="radio" name="item" id="item-three" hidden />
    <label for="item-three">Item 3</label>
    <div>
      <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Debitis praesentium, perspiciatis optio repellat quos maiores cum, tempore veniam ratione delectus quae ex laudantium modi. Quam sequi illo laudantium, harum odio.</p>
    </div>
  </div>
  <div>
    <input type="radio" name="item" id="item-four" hidden />
    <label for="item-four">Item 4</label>
    <div>
      <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Debitis praesentium, perspiciatis optio repellat quos maiores cum, tempore veniam ratione delectus quae ex laudantium modi. Quam sequi illo laudantium, harum odio.</p>
    </div>
  </div>
  <div>
    <input type="radio" name="item" id="item-five" hidden />
    <label for="item-five">Item 5</label>
    <div>
      <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Debitis praesentium, perspiciatis optio repellat quos maiores cum, tempore veniam ratione delectus quae ex laudantium modi. Quam sequi illo laudantium, harum odio.</p>
    </div>
  </div>
</div>

The primary CSS and CSS3 styles.

.block {
  max-width: 400px;
  width: 100%;
  height: 100%;
  float: left;
  padding: 15px;
  z-index: 10;
  background-color: #fafafa;
  overflow: hidden;
  margin: 50px auto;
}
@media screen and (max-width: 599px) {
.block { max-width: 100%; }
}
.block > div {
  display: block;
  position: relative;
  padding: 0 0 0 35px;
  border-bottom: 1px solid white;
  background-color: #e6e6e6;
  color: black;
}
.block > div:nth-child(1):before {
  content: "1";
  width: 20px;
  font-weight: bold;
  text-align: center;
  position: absolute;
  left: 0;
  top: 0;
  background-color: #466970;
  padding: 7.5px;
  margin: 0;
  color: white;
}
.block > div:nth-child(2):before {
  content: "2";
  width: 20px;
  font-weight: bold;
  text-align: center;
  position: absolute;
  left: 0;
  top: 0;
  background-color: #466970;
  padding: 7.5px;
  margin: 0;
  color: white;
}
.block > div:nth-child(3):before {
  content: "3";
  width: 20px;
  font-weight: bold;
  text-align: center;
  position: absolute;
  left: 0;
  top: 0;
  background-color: #466970;
  padding: 7.5px;
  margin: 0;
  color: white;
}
.block > div:nth-child(4):before {
  content: "4";
  width: 20px;
  font-weight: bold;
  text-align: center;
  position: absolute;
  left: 0;
  top: 0;
  background-color: #466970;
  padding: 7.5px;
  margin: 0;
  color: white;
}
.block > div:nth-child(5):before {
  content: "5";
  width: 20px;
  font-weight: bold;
  text-align: center;
  position: absolute;
  left: 0;
  top: 0;
  background-color: #466970;
  padding: 7.5px;
  margin: 0;
  color: white;
}
.block > div input + label {
  cursor: pointer;
  display: block;
  padding: 7.5px 15px;
  background-color: #a2c0c6;
  -webkit-transition: background-color 0.25s ease-in-out 0.5s, color 0.25s ease-in-out 0.5s;
  transition: background-color 0.25s ease-in-out 0.5s, color 0.25s ease-in-out 0.5s;
  color: black;
}
.block > div input ~ div {
  visibility: hidden;
  max-height: 0;
  padding: 0;
  opacity: 0;
  -webkit-transition: all 0.5s ease-in-out 0.2s, opacity 0.25s ease-in-out 0.25s, padding 0s ease-in-out 0s;
  transition: all 0.5s ease-in-out 0.2s, opacity 0.25s ease-in-out 0.25s, padding 0s ease-in-out 0s;
}
.block > div input ~ div p { padding: 0 15px; }
.block > div input:checked + label {
  background-color: #739fa8;
  -webkit-transition: background-color 0s ease-in-out 0s;
  transition: background-color 0s ease-in-out 0s;
  color: black;
}
.block > div input:checked ~ div {
  display: block;
  opacity: 1;
  visibility: visible;
  max-height: 200px;
  padding: 15px 0;
  -webkit-transition: all 0.5s ease-in-out 0.2s, opacity 0.25s ease-in-out 0.5s, padding 0s ease-in-out 0s;
  transition: all 0.5s ease-in-out 0.2s, opacity 0.25s ease-in-out 0.5s, padding 0s ease-in-out 0s;
}