.container {
  position: relative;
  width: 100%;
  max-width: 960px;
  margin: 0px auto;
  padding: 20px;
  box-sizing: border-box;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: horizontal;
  -webkit-box-direction: normal;
      -ms-flex-direction: row;
          flex-direction: row;
  -ms-flex-wrap: wrap;
      flex-wrap: wrap;
  -webkit-box-pack: center;
      -ms-flex-pack: center;
          justify-content: center;
  -webkit-box-align: center;
      -ms-flex-align: center;
          align-items: center;
}

.element-card {
  position: relative;
  width: 100px;
  height: 130px;
  -webkit-transform-style: preserve-3d;
          transform-style: preserve-3d;
  -webkit-transform: rotatey(0deg) translatex(0px) translatey(0px);
          transform: rotatey(0deg) translatex(0px) translatey(0px);
  -webkit-transition: all 0.6s cubic-bezier(0.68, -0.55, 0.265, 1.55);
  transition: all 0.6s cubic-bezier(0.68, -0.55, 0.265, 1.55);
  box-shadow: 4px 4px 20px rgba(0, 0, 0, 0.4);
  margin: 5px;
  cursor: pointer;
}
.element-card:hover {
  -webkit-transform: rotatey(45deg) translatex(0px) translatey(0px);
          transform: rotatey(45deg) translatex(0px) translatey(0px);
}
.element-card.open {
  width: 300px;
  height: 360px;
  -webkit-transform: rotatey(-180deg) translatex(0px) translatey(0px);
          transform: rotatey(-180deg) translatex(0px) translatey(0px);
}
.element-card .front-facing {
  -webkit-transform: rotateY(0deg) translateZ(2px);
          transform: rotateY(0deg) translateZ(2px);
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  background-color: #ecf0f1;
  border: 2px white solid;
  border-radius: 5px;
}
.element-card .front-facing .abr {
  width: 100%;
  position: absolute;
  top: 50%;
  left: 0;
  font-size: 42px;
  margin: -35px 0 0 0;
  text-align: center;
  color: #3498db;
}
.element-card .front-facing .title {
  width: 100%;
  position: absolute;
  top: 50%;
  left: 0;
  text-transform: uppercase;
  font-size: 12px;
  margin: 15px 0 0 0;
  text-align: center;
  color: #3498db;
}
.element-card .front-facing .atomic-number {
  position: absolute;
  top: 10px;
  left: 10px;
  font-size: 12px;
  color: #2980b9;
}
.element-card .front-facing .atomic-mass {
  position: absolute;
  bottom: 10px;
  right: 10px;
  font-size: 12px;
  color: #2980b9;
}
.element-card .back-facing {
  -webkit-transform: rotateY(180deg) translateZ(0px);
          transform: rotateY(180deg) translateZ(0px);
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
      -ms-flex-direction: column;
          flex-direction: column;
  -ms-flex-wrap: nowrap;
      flex-wrap: nowrap;
  -webkit-box-pack: center;
      -ms-flex-pack: center;
          justify-content: center;
  -webkit-box-align: center;
      -ms-flex-align: center;
          align-items: center;
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  background-color: #ecf0f1;
  border: 2px white solid;
  border-radius: 5px;
  padding: 20px;
  text-align: center;
  overflow: hidden;
}
.element-card .back-facing p {
  font-size: 14px;
  margin: 0;
    color: #2980b9;
}
.element-card .back-facing a.btn {
  display: inline-block;
  background-color: white;
  padding: 5px 15px;
  margin: 20px 0 0 0;
  color: #ccc;
  background-color: #3498db;
  text-decoration: none;
  border-radius: 3px;
}
.element-card .back-facing a.btn:hover, .element-card .back-facing a.btn:focus {
  color: #fff;
  background-color: #2980b9;
}