header.css

/* header navigation styling */

header {
  position: fixed;
  width: 100%;
  z-index: 100;
  background-color: rgba(95, 158, 160, 0.5);
}

header nav ul {
  padding: 0.6rem 2rem;
  max-width: 640px;
  margin-left: auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  list-style: none;
}

header ul a {
  text-decoration: none;
  color: #fff;
  padding: 0rem 0.7rem;
  text-transform: uppercase;
  font-size: 1.1rem;
  position: relative;
  /* needed for the hover effect to work */
  text-shadow: 0 -3px 0 #3b3b3b;
}

header ul a:hover {
  cursor: pointer;
}

header ul a::before {
  content: '';
  position: absolute;
  bottom: 0;
  width: 0;
  left: 50%;
  /* Center the underline */
  transform: translateX(-50%);
  height: 2px;
  background-color: white;
  transition: width 0.3s ease;
}

header ul a:hover::before {
  width: 80%;
}

/* TODO: show hamburger for mobile. Currently not used. */
.hamburger {
  padding-left: 1.5rem;
  display: none;
}

.hamburger a {
  padding: 0;
  width: 37px;
  height: 37px;
  display: flex;
  justify-content: center;
  align-items: center;
  border-radius: 50%;
  background-color: rgba(73, 118, 117, 0.7);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.hamburger a .bar {
  position: relative;
  /* allows us to use position absolute for the before and after bars */
  width: 52%;
  height: 1.5px;
  background-color: #fff;
  border-radius: 2px;
}

.hamburger a .bar::before,
.hamburger a .bar::after {
  content: "";
  position: absolute;
  left: 50%;
  /* centers them */
  transform: translateX(-50%);
  /* moves them back left by 50% of their width */
  width: 70%;
  /* 60% of .bar's width */
  height: 100%;
  /* same height as .bar */
  background-color: inherit;
  /* same as .bar */
  border-radius: 2px;
}

.hamburger .bar::before {
  top: -5px;
}

.hamburger .bar::after {
  top: 5px;
}

/* footer */
footer {
  text-align: center;
}

footer p {
  font-size: 0.8rem;
  padding: 10px;
}

@media (max-width: 768px) {
  header ul a {
    font-size: 0.9rem;
  }

  header nav ul {
    padding: 0.6rem 1.2rem;
  }
}