html, body {
  margin: 0;
  width: 100%;
  height: 100%;
  display: flex;
  background-color: #292929;
}

nav {
  width: 319px;
  margin: auto;
  position: relative;
}

nav a {
  position: relative;
  width: 33.33%;
  display: table-cell;
  text-align: center;
  color: #949494;
  text-decoration: none;
  font-weight: bold;
  padding: 10px 20px;
  transition: .2s ease color;
}

nav a::before, nav a::after {
  content: '';
  position: absolute;
  border-radius: 50%;
  transform: scale(0);
  transition: .2s ease transform;
}

nav a::before {
  top: 0;
  left: 10px;
  width: 4px;
  height: 4px;
}

nav a::after {
  top: 5px;
  left: 18px;
  width: 4px;
  height: 4px;
}

nav a:nth-child(1)::before {
  background-color: yellow;
}

nav a:nth-child(1)::after {
  background-color: red;
}

nav a:nth-child(2)::before {
  background-color: #00e2ff;
}

nav a:nth-child(2)::after {
  background-color: #89ff00;
}

nav a:nth-child(3)::before {
  background-color: purple;
}

nav a:nth-child(3)::after {
  background-color: palevioletred;
}

nav a:nth-child(1):hover ~ #scroll {
  background-image: linear-gradient(130deg, yellow, red);
}

nav a:nth-child(2):hover ~ #scroll {
  left: 34%;
  background-image: linear-gradient(130deg, #00e2ff, #89ff00);
}

nav a:nth-child(3):hover ~ #scroll {
  left: 70%;
  background-image: linear-gradient(130deg, purple, palevioletred);
}

nav a:hover {
  color: #fff;
}

nav a:hover::before, nav a:hover::after {
  transform: scale(1);
}

#scroll {
  position: absolute;
  left: 5%;
  bottom: 0;
  width: 30px;
  height: 3px;
  background-color: #fff;
  border-radius: 5px;
  transition: .2s ease left;
}