:root {
  color-scheme: dark;
  font-family: "IBM Plex Sans", "Avenir Next", "Segoe UI", sans-serif;
  line-height: 1.5;
  font-weight: 400;

  --bg: #0d1117;
  --panel: #151b23;
  --panel-hover: #1a2230;
  --border: #2b3442;
  --text: #edf2f7;
  --muted: #9aa6b2;
  --accent: #84d7ff;
}

* {
  box-sizing: border-box;
}

html,
body {
  min-height: 100%;
  margin: 0;
  background: var(--bg);
  color: var(--text);
}

body {
  min-width: 20rem;
}

a {
  color: inherit;
}

h1,
h2,
h3,
p {
  margin: 0;
}

button,
input,
textarea {
  font: inherit;
}

.app-shell {
  width: min(72rem, 100%);
  margin: 0 auto;
  padding: 2rem 1rem 3rem;
}

.page-header,
.page-section,
.panel,
.page-message {
  border: 0.0625rem solid var(--border);
  background: var(--panel);
  border-radius: 0.9rem;
}

.page-header,
.page-section,
.page-message {
  padding: 1.25rem;
}

.page-header {
  margin-bottom: 1rem;
}

.page-header h1,
.thread-header h1,
.page-message h1 {
  font-size: clamp(1.6rem, 3vw, 2.4rem);
  line-height: 1.1;
}

.page-kicker {
  margin-bottom: 0.35rem;
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

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

.section-header {
  margin-bottom: 0.9rem;
}

.section-header h2,
.subsection-header h2 {
  font-size: 1.1rem;
}

.subsection-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.card-grid,
.stack,
.reply-list {
  display: grid;
  gap: 0.75rem;
}

.card-grid,
.two-column-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.card,
.discussion-preview-card,
.reply-card {
  border: 0.0625rem solid var(--border);
  border-radius: 0.75rem;
  background: #111722;
}

.card,
.reply-card {
  padding: 1rem;
}

.course-card-button {
  width: 100%;
  cursor: pointer;
  text-align: left;
  color: inherit;
}

.course-card-button:hover,
.course-card-button:focus-visible {
  background: var(--panel-hover);
  outline: none;
}

.card h3,
.discussion-preview-card h3 {
  margin-bottom: 0.35rem;
  font-size: 1rem;
}

.discussion-preview-card {
  width: 100%;
  padding: 1rem;
  cursor: pointer;
  text-align: left;
  color: inherit;
}

.discussion-preview-card:hover,
.discussion-preview-card:focus-visible {
  background: var(--panel-hover);
  outline: none;
}

.muted-copy,
.meta-line,
.empty-state {
  color: var(--muted);
}

.muted-copy {
  max-width: 44rem;
}

.meta-line {
  margin-top: 0.5rem;
  font-size: 0.9rem;
}

.empty-state {
  padding: 0.25rem 0;
}

.back-link,
.secondary-link,
.compose-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 0.65rem;
  border: 0.0625rem solid var(--border);
  padding: 0.65rem 0.85rem;
  text-decoration: none;
}

.back-link {
  margin-bottom: 1rem;
  background: transparent;
  color: var(--text);
  cursor: pointer;
}

.thread-view {
  display: grid;
  gap: 1rem;
}

.panel {
  padding: 1.25rem;
}

.thread-header {
  margin-bottom: 1rem;
}

.panel-actions {
  margin-top: 1rem;
}

.thread-copy {
  display: grid;
  gap: 0.85rem;
}

.reply-author {
  font-weight: 600;
}

.outline-list,
.lesson-list {
  display: grid;
  gap: 1rem;
}

.outline-chapter h3 {
  margin-bottom: 0.75rem;
  font-size: 1rem;
}

.lesson-row {
  display: grid;
  grid-template-columns: 2.5rem minmax(0, 1fr);
  gap: 0.75rem;
  align-items: start;
  border-top: 0.0625rem solid var(--border);
  padding-top: 0.75rem;
}

.lesson-row-button {
  width: 100%;
  cursor: pointer;
  text-align: left;
  color: inherit;
  background: transparent;
}

.lesson-row-button:hover,
.lesson-row-button:focus-visible {
  background: var(--panel-hover);
  outline: none;
  border-radius: 0.5rem;
}

.lesson-row:first-child {
  border-top: 0;
  padding-top: 0;
}

.lesson-index {
  color: var(--muted);
  font-size: 0.9rem;
}

.lesson-title {
  font-weight: 600;
}

.lesson-summary {
  margin-top: 0.35rem;
  color: var(--muted);
}

.markdown-content {
  display: grid;
  gap: 0.85rem;
}

.markdown-content > :first-child {
  margin-top: 0;
}

.markdown-content > :last-child {
  margin-bottom: 0;
}

.markdown-content h1,
.markdown-content h2,
.markdown-content h3,
.markdown-content h4 {
  line-height: 1.15;
}

.markdown-content h1 {
  font-size: 1.8rem;
}

.markdown-content h2 {
  font-size: 1.35rem;
}

.markdown-content h3 {
  font-size: 1.1rem;
}

.markdown-content p,
.markdown-content li,
.markdown-content blockquote {
  color: var(--text);
}

.markdown-content ul,
.markdown-content ol {
  margin: 0;
  padding-left: 1.4rem;
}

.markdown-content li + li {
  margin-top: 0.35rem;
}

.markdown-content code {
  border-radius: 0.35rem;
  padding: 0.12rem 0.35rem;
  background: #0b1017;
  font-family: "IBM Plex Mono", "SFMono-Regular", monospace;
  font-size: 0.92em;
}

.markdown-content pre {
  overflow-x: auto;
  margin: 0;
  border: 0.0625rem solid var(--border);
  border-radius: 0.75rem;
  padding: 0.85rem 0.95rem;
  background: #0b1017;
}

.markdown-content pre code {
  padding: 0;
  background: transparent;
}

.markdown-content blockquote {
  margin: 0;
  border-left: 0.2rem solid var(--accent);
  padding-left: 0.9rem;
}

.markdown-content a {
  color: var(--accent);
}

.markdown-content hr {
  width: 100%;
  height: 0.0625rem;
  margin: 0;
  border: 0;
  background: var(--border);
}

.compose-box {
  display: grid;
  gap: 0.85rem;
}

.compose-input {
  width: 100%;
  min-height: 9rem;
  resize: vertical;
  border: 0.0625rem solid var(--border);
  border-radius: 0.75rem;
  padding: 0.85rem 0.95rem;
  color: var(--text);
  background: #0f141d;
}

.compose-actions {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.compose-button {
  color: #7a8696;
  background: #101722;
  cursor: not-allowed;
}

.secondary-link {
  color: var(--accent);
}

@media (max-width: 48rem) {
  .card-grid,
  .two-column-grid {
    grid-template-columns: 1fr;
  }

  .compose-actions,
  .subsection-header {
    align-items: flex-start;
    flex-direction: column;
  }
}