:root {
  --bg-dark: #0d1117;
  --bg-card: #161b22;
  --bg-card-hover: #1c2128;
  --border-color: #30363d;
  --text-main: #c9d1d9;
  --text-muted: #8b949e;
  --text-bright: #f0f6fc;
  --copper-primary: #d97736;
  --copper-glow: #f0883e;
  --gold: #ffd700;
  --cyan: #58a6ff;
  --green: #3fb950;
  --red: #f85149;
  --purple: #a371f7;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background-color: var(--bg-dark);
  color: var(--text-main);
  font-family: var(--font-sans);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Site switcher: this app is one section of a larger site, so give visitors a
   visible way back to the solver instead of the browser's back button. */
.site-switch {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding: 0.4rem 2rem;
  background-color: #0b0e14;
  border-bottom: 1px solid var(--border-color);
  font-size: 0.8rem;
  color: var(--text-muted);
}

.site-switch a {
  color: var(--cyan);
  text-decoration: none;
  font-weight: 600;
}

.site-switch a:hover {
  text-decoration: underline;
}

/* Header & Nav */
header {
  background-color: var(--bg-card);
  border-bottom: 1px solid var(--border-color);
  padding: 1rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  position: sticky;
  top: 0;
  z-index: 100;
}

.logo-container {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo-badge {
  background: linear-gradient(135deg, var(--copper-primary), #8c3a00);
  color: #fff;
  font-weight: 900;
  padding: 6px 12px;
  border-radius: 6px;
  font-family: var(--font-mono);
  letter-spacing: 2px;
  box-shadow: 0 0 10px rgba(217, 119, 54, 0.4);
}

.logo-title h1 {
  font-size: 1.25rem;
  color: var(--text-bright);
  font-weight: 700;
}

.logo-title p {
  font-size: 0.75rem;
  color: var(--text-muted);
}

nav {
  display: flex;
  gap: 8px;
}

.nav-tab {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid transparent;
  padding: 8px 16px;
  border-radius: 6px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
}

.nav-tab:hover {
  color: var(--text-bright);
  background-color: var(--border-color);
}

.nav-tab.active {
  color: var(--copper-glow);
  background-color: var(--bg-dark);
  border-color: var(--copper-primary);
  box-shadow: 0 0 8px rgba(240, 136, 62, 0.2);
}

/* Main Container */
main {
  flex: 1;
  padding: 2rem;
  max-width: 1400px;
  margin: 0 auto;
  width: 100%;
}

.tab-pane {
  display: none;
}

.tab-pane.active {
  display: block;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Cipher Explorer */
.cipher-explorer-layout {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 24px;
}

.cipher-sidebar {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 16px;
  max-height: calc(100vh - 160px);
  overflow-y: auto;
}

.sidebar-category-title {
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 700;
  letter-spacing: 1.5px;
  margin: 16px 0 8px;
}

.sidebar-category-title:first-child {
  margin-top: 0;
}

.cipher-nav-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 12px;
  border-radius: 6px;
  cursor: pointer;
  margin-bottom: 4px;
  transition: all 0.15s ease;
}

.cipher-nav-item:hover {
  background-color: var(--bg-card-hover);
}

.cipher-nav-item.active {
  background-color: rgba(217, 119, 54, 0.15);
  border-left: 3px solid var(--copper-primary);
}

.cipher-name {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-bright);
}

.cipher-badge {
  font-size: 0.7rem;
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 700;
}

.badge-solved {
  background-color: rgba(63, 185, 80, 0.2);
  color: var(--green);
  border: 1px solid rgba(63, 185, 80, 0.4);
}

.badge-frontier {
  background-color: rgba(240, 136, 62, 0.2);
  color: var(--copper-glow);
  border: 1px solid rgba(240, 136, 62, 0.4);
}

.badge-custody {
  background-color: rgba(88, 166, 255, 0.2);
  color: var(--cyan);
  border: 1px solid rgba(88, 166, 255, 0.4);
}

.badge-unsolved {
  background-color: rgba(248, 81, 73, 0.2);
  color: var(--red);
  border: 1px solid rgba(248, 81, 73, 0.4);
}

/* Detail Card */
.cipher-detail-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 24px;
}

.detail-header {
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 16px;
  margin-bottom: 20px;
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
}

.detail-title h2 {
  font-size: 1.5rem;
  color: var(--text-bright);
  margin-bottom: 4px;
}

.detail-title p {
  color: var(--text-muted);
  font-size: 0.85rem;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin-bottom: 24px;
}

.stat-box {
  background-color: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 12px;
  text-align: center;
}

.stat-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1px;
}

.stat-value {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--cyan);
  font-family: var(--font-mono);
  margin-top: 4px;
}

.text-section {
  margin-bottom: 20px;
}

.text-section h3 {
  font-size: 0.9rem;
  text-transform: uppercase;
  color: var(--text-muted);
  letter-spacing: 1px;
  margin-bottom: 8px;
}

.code-display {
  background-color: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 14px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  word-break: break-all;
  line-height: 1.5;
  color: #e6edf3;
  position: relative;
}

.code-display.plaintext-highlight {
  color: #7ee787;
  border-color: rgba(63, 185, 80, 0.4);
}

/* Copper Sculpture Visualizer */
.sculpture-container {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 24px;
  text-align: center;
}

.sculpture-svg-wrapper {
  margin: 20px 0;
  overflow-x: auto;
}

/* Book Reader */
.book-reader-container {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 24px;
}

.book-toc {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 16px;
  max-height: calc(100vh - 160px);
  overflow-y: auto;
}

.book-toc h3 {
  font-size: 0.9rem;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.toc-item {
  padding: 8px 12px;
  border-radius: 4px;
  font-size: 0.85rem;
  color: var(--text-main);
  cursor: pointer;
  margin-bottom: 4px;
  transition: all 0.15s ease;
}

.toc-item:hover {
  background-color: var(--bg-card-hover);
  color: var(--text-bright);
}

.toc-item.active {
  background-color: rgba(88, 166, 255, 0.15);
  color: var(--cyan);
  font-weight: 600;
}

.book-content {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 36px;
  line-height: 1.8;
  max-height: calc(100vh - 160px);
  overflow-y: auto;
}

.book-content h1, .book-content h2, .book-content h3 {
  color: var(--text-bright);
  margin-top: 1.5rem;
  margin-bottom: 0.75rem;
}

.book-content p {
  margin-bottom: 1rem;
}

/* Workbench */
.workbench-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.workbench-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 24px;
}

textarea.tool-input {
  width: 100%;
  height: 160px;
  background-color: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  color: var(--text-bright);
  font-family: var(--font-mono);
  padding: 12px;
  font-size: 0.85rem;
  resize: vertical;
  margin-bottom: 16px;
}

textarea.tool-input:focus {
  outline: none;
  border-color: var(--cyan);
}

button.btn-primary {
  background: linear-gradient(135deg, var(--copper-primary), #8c3a00);
  color: #fff;
  border: none;
  padding: 10px 20px;
  font-weight: 700;
  border-radius: 6px;
  cursor: pointer;
  transition: opacity 0.2s ease;
}

button.btn-primary:hover {
  opacity: 0.9;
}

/* GitHub Guide */
.github-guide-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 32px;
  max-width: 900px;
  margin: 0 auto;
}

.github-steps {
  margin: 24px 0;
}

.step-box {
  background-color: var(--bg-dark);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 16px;
  margin-bottom: 16px;
}

.step-box h3 {
  color: var(--cyan);
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.step-box pre {
  background-color: #000;
  padding: 10px;
  border-radius: 4px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: #7ee787;
  overflow-x: auto;
}

footer {
  border-top: 1px solid var(--border-color);
  background-color: var(--bg-card);
  padding: 1.5rem 2rem;
  text-align: center;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.frontier-display {
  color: var(--copper-glow);
  border-color: rgba(240, 136, 62, 0.55);
  white-space: pre-wrap;
  word-break: normal;
}

[hidden] {
  display: none !important;
}

/* Responsive layout ------------------------------------------------------- */
/* The explorer is used on small screens as often as it is on a desktop. Keep
   navigation finger-sized, let long cipher text wrap, and turn desktop sidebars
   into horizontally scrollable selectors rather than forcing a cramped column. */
html {
  min-width: 0;
}

body {
  overflow-x: hidden;
}

button,
input,
select,
textarea {
  font: inherit;
}

.title-compact,
.nav-label-compact {
  display: none;
}

.code-display {
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}

code {
  overflow-wrap: anywhere;
}

@media (max-width: 1080px) {
  header {
    align-items: flex-start;
    gap: 0.9rem;
  }

  nav {
    max-width: 54%;
    overflow-x: auto;
    overscroll-behavior-x: contain;
    padding-bottom: 2px;
    scrollbar-width: thin;
  }

  .nav-tab {
    flex: 0 0 auto;
    white-space: nowrap;
  }

  .cipher-explorer-layout {
    grid-template-columns: 250px minmax(0, 1fr);
    gap: 16px;
  }

  .book-reader-container {
    grid-template-columns: 220px minmax(0, 1fr);
    gap: 16px;
  }

  .cipher-detail-card,
  .book-content,
  .workbench-card,
  .sculpture-container {
    min-width: 0;
  }
}

@media (max-width: 760px) {
  .site-switch {
    padding: 0.4rem 0.85rem;
    font-size: 0.75rem;
  }

  header {
    position: static;
    display: block;
    padding: 0.8rem 0.85rem 0.65rem;
  }

  .logo-container {
    gap: 0.6rem;
    min-width: 0;
  }

  .logo-badge {
    padding: 5px 8px;
    font-size: 0.82rem;
    letter-spacing: 1px;
    flex: 0 0 auto;
  }

  .logo-title {
    min-width: 0;
  }

  .logo-title h1 {
    font-size: 1rem;
    line-height: 1.2;
  }

  .logo-title p {
    font-size: 0.7rem;
    line-height: 1.3;
    margin-top: 0.18rem;
  }

  .title-wide,
  .nav-label-wide {
    display: none;
  }

  .title-compact,
  .nav-label-compact {
    display: inline;
  }

  nav {
    max-width: none;
    width: calc(100% + 1.7rem);
    margin: 0.75rem -0.85rem -0.05rem;
    padding: 0 0.85rem 0.45rem;
    gap: 0.45rem;
    -webkit-overflow-scrolling: touch;
  }

  .nav-tab {
    min-height: 2.5rem;
    padding: 0.5rem 0.75rem;
    font-size: 0.82rem;
  }

  main {
    padding: 0.85rem;
  }

  .cipher-explorer-layout,
  .book-reader-container,
  .workbench-grid {
    display: block;
  }

  .cipher-sidebar {
    display: flex;
    align-items: stretch;
    gap: 0.45rem;
    max-height: none;
    margin-bottom: 0.85rem;
    overflow-x: auto;
    overflow-y: hidden;
    padding: 0.55rem;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: thin;
  }

  .sidebar-category-title {
    align-self: center;
    flex: 0 0 auto;
    margin: 0;
    padding: 0 0.3rem;
    font-size: 0.65rem;
    white-space: nowrap;
  }

  .cipher-nav-item {
    flex: 0 0 9.75rem;
    min-height: 3.75rem;
    margin: 0;
    padding: 0.55rem 0.65rem;
    gap: 0.45rem;
  }

  .cipher-name {
    font-size: 0.78rem;
    line-height: 1.25;
  }

  .cipher-badge {
    flex: 0 0 auto;
    font-size: 0.62rem;
  }

  .cipher-detail-card,
  .sculpture-container,
  .workbench-card,
  .github-guide-card {
    padding: 1rem;
    border-radius: 7px;
  }

  .detail-header {
    display: block;
    padding-bottom: 0.85rem;
    margin-bottom: 1rem;
  }

  .detail-title h2 {
    font-size: 1.25rem;
    line-height: 1.22;
  }

  .detail-title p {
    font-size: 0.78rem;
    overflow-wrap: anywhere;
  }

  .detail-header > div:last-child {
    margin-top: 0.65rem;
  }

  .stats-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.55rem;
    margin-bottom: 1rem;
  }

  .stat-box {
    padding: 0.6rem 0.35rem;
  }

  .stat-label {
    font-size: 0.62rem;
    letter-spacing: 0.45px;
    line-height: 1.25;
  }

  .stat-value {
    font-size: 1rem;
  }

  .text-section {
    margin-bottom: 1rem;
  }

  .text-section h3 {
    font-size: 0.72rem;
    letter-spacing: 0.7px;
  }

  .code-display {
    padding: 0.75rem;
    font-size: 0.76rem;
    line-height: 1.55;
  }

  .sculpture-container h2,
  .workbench-card h2,
  .github-guide-card h2 {
    font-size: 1.2rem;
    line-height: 1.25;
  }

  .sculpture-svg-wrapper {
    margin: 1rem 0;
    padding-bottom: 0.5rem;
    -webkit-overflow-scrolling: touch;
  }

  .sculpture-svg-wrapper img {
    width: 900px;
    max-width: none !important;
  }

  .book-toc {
    max-height: none;
    margin-bottom: 0.85rem;
    overflow: hidden;
    padding: 0.75rem;
  }

  .book-toc h3 {
    margin-bottom: 0.55rem;
  }

  #book-toc-list {
    display: flex;
    gap: 0.45rem;
    overflow-x: auto;
    padding-bottom: 0.25rem;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: thin;
  }

  .toc-item {
    flex: 0 0 12.5rem;
    min-height: 2.75rem;
    display: flex;
    align-items: center;
    margin: 0;
    padding: 0.55rem 0.65rem;
    font-size: 0.78rem;
    line-height: 1.25;
  }

  .book-content {
    max-height: none;
    overflow: visible;
    padding: 1rem;
    line-height: 1.65;
  }

  .book-content h1,
  .book-content h2,
  .book-content h3 {
    line-height: 1.25;
  }

  .book-content p,
  .book-content li {
    overflow-wrap: anywhere;
  }

  .workbench-card + .workbench-card {
    margin-top: 0.85rem;
  }

  textarea.tool-input {
    height: 9rem;
    font-size: 0.8rem;
  }

  .step-box {
    padding: 0.85rem;
  }

  .step-box h3 {
    align-items: flex-start;
    line-height: 1.3;
  }

  .step-box pre {
    font-size: 0.75rem;
  }

  footer {
    padding: 1rem;
    font-size: 0.72rem;
    line-height: 1.45;
  }
}

@media (max-width: 390px) {
  .site-switch span {
    display: none;
  }

  .site-switch {
    justify-content: flex-start;
  }

  .logo-title p {
    display: none;
  }

  .nav-tab {
    padding-inline: 0.65rem;
  }

  .cipher-nav-item {
    flex-basis: 9.1rem;
  }

  .stats-grid {
    gap: 0.4rem;
  }
}

/* Official Paradigm source link in the cipher detail header. */
.challenge-link {
  display: inline-flex;
  align-items: center;
  width: fit-content;
  margin-top: 0.55rem;
  color: var(--cyan);
  font-size: 0.8rem;
  font-weight: 700;
  text-decoration: none;
}

.challenge-link:hover,
.challenge-link:focus-visible {
  color: var(--text-bright);
  text-decoration: underline;
}

@media (max-width: 760px) {
  .challenge-link {
    min-height: 2.5rem;
    margin-top: 0.35rem;
    font-size: 0.78rem;
  }
}