html, body {
  height: 100%;
}

body {
  display: -webkit-box;
  display: flex;
  -webkit-box-align: center;
          align-items: center;
  -webkit-box-pack: center;
          justify-content: center;
  /*background-color: #ecf0f1;*/
  background-color: #00ffee;
}
.heart {
  position: relative;
}
.heart,
.heart:before,
.heart:after {
  display: block;
  width: 50px;
  height: 50px;
  background-color: #39f;
  -webkit-transform: rotateZ(45deg);
          transform: rotateZ(45deg);
}
.heart:before,
.heart:after {
  content: '';
  position: absolute;
  border-radius: 50%;
}
.heart:before {
  -webkit-transform: translateX(-50%);
          transform: translateX(-50%);
  -webkit-animation: animX 3s infinite 0.75s;
          animation: animX 3s infinite 0.75s;
}
.heart:after {
  -webkit-transform: translateY(-50%);
          transform: translateY(-50%);
  -webkit-animation: animY 3s infinite;
          animation: animY 3s infinite;
}
@-webkit-keyframes animX {
  0%, 25% {
    -webkit-transform: translateX(-50%);
            transform: translateX(-50%);
  }
  50%, 75% {
    -webkit-transform: translateX(50%);
            transform: translateX(50%);
  }
}
@keyframes animX {
  0%, 25% {
    -webkit-transform: translateX(-50%);
            transform: translateX(-50%);
  }
  50%, 75% {
    -webkit-transform: translateX(50%);
            transform: translateX(50%);
  }
}
@-webkit-keyframes animY {
  0%, 25% {
    -webkit-transform: translateY(-50%);
            transform: translateY(-50%);
  }
  50%, 75% {
    -webkit-transform: translateY(50%);
            transform: translateY(50%);
  }
}
@keyframes animY {
  0%, 25% {
    -webkit-transform: translateY(-50%);
            transform: translateY(-50%);
  }
  50%, 75% {
    -webkit-transform: translateY(50%);
            transform: translateY(50%);
  }
}