/* Reset */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: system-ui, -apple-system, sans-serif;
  background-color: #475569; /* slate-600 */
  color: #e2e8f0; /* slate-200 */
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Nav */
nav {
  padding: 0.75rem 0.5rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.nav-link {
  display: inline-block;
  padding: 0.5rem 0.75rem;
  border-radius: 0.375rem;
  color: #cbd5e1; /* slate-300 */
  text-decoration: none;
  font-weight: 500;
  transition: color 0.15s, background-color 0.15s;
}

.nav-link:hover,
.nav-link:focus,
.nav-link.active {
  color: #fff;
  background-color: #374151; /* gray-700 */
  outline: none;
}

/* Main content */
main {
  flex: 1;
  max-width: 48rem;
  width: 100%;
  margin: 0 auto;
  padding: 2rem 1rem;
}

/* Home */
.home h1 {
  font-size: 1.875rem;
  font-weight: 700;
  text-decoration: underline;
  margin-bottom: 0.75rem;
}

.home h2 {
  font-weight: 700;
}

/* Whoami */
.whoami {
  display: flex;
  justify-content: center;
  padding-top: 2rem;
}

.whoami-content {
  max-width: 40rem;
}

.whoami-content p {
  font-size: 1.25rem;
  color: #e2e8f0; /* slate-200 */
  margin-bottom: 1.75rem;
}

/* Link styles */
.link-orange {
  color: inherit;
  text-decoration: underline;
  text-decoration-color: #ea580c; /* orange-600 */
  transition: opacity 0.15s;
}

.link-orange:hover { opacity: 0.7; }

.link-teal {
  color: inherit;
  text-decoration: underline;
  text-decoration-color: #2dd4bf; /* teal-400 */
  transition: opacity 0.15s;
}

.link-teal:hover { opacity: 0.7; }

.link-light {
  color: inherit;
  text-decoration: underline;
  text-decoration-color: #ffedd5; /* orange-100 */
  transition: opacity 0.15s;
}

.link-light:hover { opacity: 0.7; }

/* Contact */
.contact-list {
  list-style: none;
  padding: 2rem;
}

.contact-list li {
  color: #14b8a6; /* teal-500 */
  margin-bottom: 0.5rem;
}

.contact-list a {
  color: #ffedd5; /* orange-100 */
  text-decoration: underline;
  text-decoration-color: #f97316; /* orange-500 */
  padding-bottom: 0.25rem;
  transition: opacity 0.15s;
}

.contact-list a:hover {
  opacity: 0.7;
}

/* Books page */
.books-header {
  font-size: 1.5rem;
  font-weight: 700;
  color: #fff;
  text-align: center;
  padding-top: 2.5rem;
  margin-bottom: 1.5rem;
}

.books-layout {
  display: flex;
  gap: 1.75rem;
  padding-top: 1.75rem;
}

.year-filters {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.btn-year {
  background-color: #ffedd5; /* orange-100 */
  font-weight: 700;
  padding: 0.25rem 0.5rem;
  border: none;
  border-bottom: 4px solid transparent;
  border-radius: 0.25rem;
  cursor: pointer;
  transition: border-bottom-color 0.15s, background-color 0.15s;
}

.btn-year:hover {
  border-bottom-color: #f97316; /* orange-500 */
}

.btn-year.active {
  border-bottom-color: #ea580c; /* orange-600 */
  background-color: #fed7aa; /* orange-200 */
}

.btn-reset {
  background-color: #14b8a6; /* teal-500 */
  color: #fff;
  font-weight: 700;
  padding: 0.25rem 0.5rem;
  border: none;
  border-radius: 0.25rem;
  cursor: pointer;
  transition: background-color 0.15s;
}

.btn-reset:hover {
  background-color: #0d9488; /* teal-600 */
}

.book-list {
  list-style: none;
  color: #fdba74; /* orange-300 */
}

.book-list li {
  font-size: 0.875rem;
  margin-bottom: 0.5rem;
}

.year-heading {
  font-weight: 700;
  font-size: 1rem;
  color: #fff;
  margin-top: 1rem;
  margin-bottom: 0.25rem;
}

.year-heading:first-child {
  margin-top: 0;
}

/* Footer */
footer {
  max-width: 48rem;
  margin: 0 auto;
  padding: 2rem 1rem;
  font-size: 0.875rem;
  color: #94a3b8; /* slate-400 */
}

footer hr {
  border: none;
  border-top: 1px solid #64748b; /* slate-500 */
  margin-bottom: 0.75rem;
}

.footer-sep {
  margin: 0 0.375rem;
}

footer a {
  color: #94a3b8; /* slate-400 */
  text-decoration: none;
  transition: color 0.15s;
}

footer a:hover {
  color: #e2e8f0; /* slate-200 */
}

/* 404 */
.error-page {
  text-align: center;
  padding-top: 4rem;
}

.error-page h1 {
  font-size: 4rem;
  font-weight: 700;
  color: #f97316; /* orange-500 */
  margin-bottom: 0.5rem;
}

.error-page p {
  font-size: 1.25rem;
  margin-bottom: 1rem;
}

/* Responsive */
@media (max-width: 640px) {
  .books-layout {
    flex-direction: column;
  }

  .year-filters {
    flex-direction: row;
    flex-wrap: wrap;
  }

  nav {
    flex-direction: column;
  }
}