@import url("https://fonts.googleapis.com/css?family=DM+Sans:500,700&display=swap");
* {
  box-sizing: border-box;
}

body {
  text-align: center;
  display: -webkit-box;
  display: flex;
  height: 100vh;
  width: 100%;
  -webkit-box-pack: center;
          justify-content: center;
  -webkit-box-align: center;
          align-items: center;
  padding: 0 20px;
  background-image: url("https://www.toptal.com/designers/subtlepatterns/patterns/debut_light.png");
}

.nav {
  display: -webkit-inline-box;
  display: inline-flex;
  position: relative;
  overflow: hidden;
  max-width: 100%;
  background-color: #fff;
  padding: 0 20px;
  border-radius: 40px;
  box-shadow: 0 10px 40px rgba(159, 162, 177, 0.8);
}

.nav-item {
  color: #83818c;
  padding: 20px;
  text-decoration: none;
  -webkit-transition: .3s;
  transition: .3s;
  margin: 0 6px;
  z-index: 1;
  font-family: 'DM Sans', sans-serif;
  font-weight: 500;
  position: relative;
}
.nav-item:before {
  content: "";
  position: absolute;
  bottom: -6px;
  left: 0;
  width: 100%;
  height: 5px;
  background-color: #dfe2ea;
  border-radius: 8px 8px 0 0;
  opacity: 0;
  -webkit-transition: .3s;
  transition: .3s;
}

.nav-item:not(.is-active):hover:before {
  opacity: 1;
  bottom: 0;
}

.nav-item:not(.is-active):hover {
  color: #333;
}

.nav-indicator {
  position: absolute;
  left: 0;
  bottom: 0;
  height: 4px;
  -webkit-transition: .4s;
  transition: .4s;
  height: 5px;
  z-index: 1;
  border-radius: 8px 8px 0 0;
}

@media (max-width: 580px) {
  .nav {
    overflow: auto;
  }
}

const indicator = document.querySelector('.nav-indicator');
const items = document.querySelectorAll('.nav-item');

function handleIndicator(el) {
  items.forEach(item => {
    item.classList.remove('is-active');
    item.removeAttribute('style');
  });

  indicator.style.width = `${el.offsetWidth}px`;
  indicator.style.left = `${el.offsetLeft}px`;
  indicator.style.backgroundColor = el.getAttribute('active-color');

  el.classList.add('is-active');
  el.style.color = el.getAttribute('active-color');
}


items.forEach((item, index) => {
  item.addEventListener('click', e => {handleIndicator(e.target);});
  item.classList.contains('is-active') && handleIndicator(item);
});