body {
  padding: 0;
  background: darkslategray;
}

.panels {
  display: flex;
  flex-direction: row;
}

.panel {
  flex: 1;
  min-height: 100vh;
  text-align: center;
  -webkit-transition: 300ms;
  transition: 300ms;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}

.circle {
  -webkit-transition: 200ms ease;
  transition: 200ms ease;
  width: 100%;
  height: 100%;
  border: solid 2px white;
  border-radius: 50%;
  flex: 1;
  background-position: center;
}

.circle-active {
  flex: 4;
  border: solid 8px darkslategray;
  border-radius: 32px;
  background: cadetblue;
}