body::before {
  content: "";
  position: fixed;
  top: 0; left: 0;
  width: 100vw; height: 100vh;
  background: url('../img/molecule-background.jpg') no-repeat center center fixed;
  background-size: cover;
  opacity: 0.07;
  z-index: -1;
}

body {
  margin: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: #f7f8fa;
  color: #222;
  line-height: 1.6;
  scroll-behavior: smooth;
}

header {
  position: fixed;
  top: 0; left: 0; right: 0;
  background: #fff;
  box-shadow: 0 2px 8px rgb(0 0 0 / 0.1);
  display: flex;
  justify-content: center;
  gap: 2rem;
  padding: 1rem 0;
  z-index: 1000;
}

header a {
  text-decoration: none;
  font-weight: 600;
  color: #0a3d62;
  transition: color 0.25s ease;
  padding: 0.3rem 0.6rem;
  border-radius: 4px;
  cursor: pointer;
}

header a:hover {
  background-color: #0a3d62;
  color: white;
}

main {
  display: flex;
  justify-content: center;
  padding: 90px 1rem 40px;
}

section {
  background: rgba(255, 255, 255, 0.8);
  width: 60vw;
  max-width: 720px;
  min-width: 320px;
  margin-bottom: 2rem;
  padding: 2rem;
  box-shadow: 0 3px 8px rgb(0 0 0 / 0.05);
  border-radius: 8px;

  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

section h2 {
  border-bottom: 3px solid #0a3d62;
  padding-bottom: 0.3rem;
  margin-bottom: 1rem;
  color: #0a3d62;
}

a.mail-link {
  color: #0a3d62;
  font-weight: 600;
}

a.mail-link:hover {
  text-decoration: underline;
}

#backToTop {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 42px;
  height: 42px;
  background-color: #0a3d62;
  border: none;
  border-radius: 50%;
  color: white;
  font-size: 22px;
  cursor: pointer;
  box-shadow: 0 3px 8px rgb(0 0 0 / 0.2);
  transition: background-color 0.3s ease;
}

#backToTop:hover {
  background-color: #062640;
}

@media (max-width: 480px) {
  header {
    gap: 1rem;
    padding: 0.7rem 0;
  }
  main {
    padding: 80px 0.5rem 30px;
  }
  section {
    width: 90vw;
    min-width: auto;
  }
}