body,
html {
  width: 100%;
  height: 100%;
  overflow: hidden;
  margin: 0;
  color: #eee;
}

* {
  position: relative;
  box-sizing: border-box;
}
body {
  background: #1d1d1d;
  font-family: sans-serif;
}

h2 {
  position: absolute;
  top: 20px;
  text-align: center;
  font-weight: normal;
}

.demo {
  width: 100%;
  height: 100%;
  background: black;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}
.box {
  width: 200px;
  height: 200px;
  background: dodgerblue;
}

.dot {
  position: absolute;
  background: rgba(255, 20, 20, 0.6);
  width: 20px;
  height: 20px;
  border-radius: 50%;
  transform: translate(-50%, -50%);
  z-index: 100;
}

.nav {
  color: #ccc;
  font-size: 1em;
  line-height: 1em;
  display: flex;
  align-items: center;
  justify-content: space-around;
  background: #1d1d1d;
  width: 80%;
  padding: 20px;
  position: absolute;
  bottom: 20px;
}

.output {
  width: 50%;
  text-align: center;
}

.output span {
  color: #d0782a;
}

input[type="radio"] {
  margin-top: -1px;
  vertical-align: middle;
}

label {
  white-space: nowrap;
}

@media screen and (max-width: 400px) {
  label:first-of-type {
    display: block;
    margin-bottom: 10px;
  }
}