:root {
  --bg: #faf8f5;
  --bg-card: #ffffff;
  --ink: #1a1814;
  --ink-muted: #5c574f;
  --accent: #c23b22;
  --accent-soft: #fde8e4;
  --accent-hover: #a32f1a;
  --border: #e8e4dc;
  --success: #2d6a4f;
  --success-bg: #e8f5ee;
  --error: #9b2226;
  --error-bg: #fdecea;
  --radius: 12px;
  --radius-lg: 20px;
  --shadow: 0 4px 24px rgba(26, 24, 20, 0.06);
  --font: "DM Sans", system-ui, sans-serif;
  --font-han: "Noto Sans SC", "PingFang SC", sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.55;
  color: var(--ink);
  background: var(--bg);
  min-height: 100vh;
}

.container {
  width: min(920px, 100% - 2rem);
  margin-inline: auto;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(250, 248, 245, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  padding: 0.85rem 0;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  color: var(--ink);
  font-weight: 700;
  font-size: 1.1rem;
}

.logo-han {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2rem;
  height: 2rem;
  background: var(--accent);
  color: #fff;
  border-radius: 8px;
  font-family: var(--font-han);
  font-size: 1.1rem;
}

.main-nav {
  display: flex;
  gap: 0.25rem;
  flex: 1;
}

.nav-link {
  background: none;
  border: none;
  font: inherit;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--ink-muted);
  padding: 0.45rem 0.85rem;
  border-radius: 8px;
  cursor: pointer;
  transition: color 0.15s, background 0.15s;
}

.nav-link:hover {
  color: var(--ink);
  background: var(--border);
}

.nav-link.active {
  color: var(--accent);
  background: var(--accent-soft);
}

.header-stats {
  display: flex;
  gap: 0.5rem;
}

.stat-pill {
  font-size: 0.8rem;
  color: var(--ink-muted);
  background: var(--bg-card);
  border: 1px solid var(--border);
  padding: 0.3rem 0.65rem;
  border-radius: 999px;
}

.stat-score {
  color: var(--success);
  border-color: #c8e6d4;
  background: var(--success-bg);
}

/* Views */
.view {
  display: none;
  padding-bottom: 3rem;
}

.view.active {
  display: block;
}

/* Hero */
.hero {
  padding: 3.5rem 0 2.5rem;
}

.hero-eyebrow {
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  margin: 0 0 0.75rem;
}

.hero h1 {
  font-size: clamp(2.2rem, 5vw, 3.2rem);
  line-height: 1.15;
  font-weight: 700;
  margin: 0 0 1rem;
  letter-spacing: -0.02em;
}

.hero-han {
  font-family: var(--font-han);
  font-weight: 500;
  color: var(--accent);
}

.hero-lead {
  font-size: 1.15rem;
  color: var(--ink-muted);
  max-width: 36rem;
  margin: 0 0 1.75rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

/* Buttons */
.btn {
  font: inherit;
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.65rem 1.25rem;
  border-radius: 10px;
  border: none;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s;
}

.btn:active {
  transform: scale(0.98);
}

.btn-primary {
  background: var(--accent);
  color: #fff;
}

.btn-primary:hover:not(:disabled) {
  background: var(--accent-hover);
}

.btn-primary:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn-ghost {
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--border);
}

.btn-ghost:hover {
  background: var(--bg-card);
}

/* Feature grid */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
  padding-bottom: 2rem;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow);
}

.feature-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  background: var(--accent-soft);
  color: var(--accent);
  font-family: var(--font-han);
  font-size: 1.25rem;
  font-weight: 700;
  border-radius: 10px;
  margin-bottom: 0.75rem;
}

.feature-card h3 {
  margin: 0 0 0.4rem;
  font-size: 1.05rem;
}

.feature-card p {
  margin: 0;
  font-size: 0.9rem;
  color: var(--ink-muted);
}

/* Page head */
.page-head {
  padding: 2rem 0 1.25rem;
}

.page-head h2 {
  margin: 0 0 0.35rem;
  font-size: 1.75rem;
}

.page-head p {
  margin: 0;
  color: var(--ink-muted);
}

/* Lessons */
.lesson-list {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.lesson-unit {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow);
}

.lesson-unit h3 {
  margin: 0;
  padding: 1rem 1.25rem;
  font-size: 1rem;
  background: var(--accent-soft);
  color: var(--accent-hover);
  border-bottom: 1px solid var(--border);
}

.vocab-table {
  width: 100%;
  border-collapse: collapse;
}

.vocab-table th,
.vocab-table td {
  padding: 0.65rem 1.25rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.vocab-table th {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--ink-muted);
  font-weight: 600;
}

.vocab-table tr:last-child td {
  border-bottom: none;
}

.vocab-han {
  font-family: var(--font-han);
  font-size: 1.35rem;
  font-weight: 500;
}

.vocab-pinyin {
  color: var(--accent);
  font-weight: 500;
}

.btn-audio {
  background: none;
  border: none;
  font-size: 1.1rem;
  cursor: pointer;
  padding: 0.2rem;
  opacity: 0.6;
  transition: opacity 0.15s;
}

.btn-audio:hover {
  opacity: 1;
}

/* Practice toolbar */
.practice-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  gap: 0.75rem 1rem;
  margin-bottom: 1.5rem;
}

.filter-label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--ink-muted);
  width: 100%;
  margin-bottom: -0.35rem;
}

.select {
  font: inherit;
  padding: 0.55rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg-card);
  min-width: 180px;
}

/* Quiz */
.quiz-area {
  margin-bottom: 1.5rem;
}

.quiz-progress {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1rem;
}

.progress-bar {
  flex: 1;
  height: 6px;
  background: var(--border);
  border-radius: 999px;
  overflow: hidden;
}

.progress-bar::after {
  content: "";
  display: block;
  height: 100%;
  width: var(--pct, 0%);
  background: var(--accent);
  border-radius: 999px;
  transition: width 0.3s ease;
}

.progress-text {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--ink-muted);
  white-space: nowrap;
}

.quiz-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow);
  min-height: 220px;
}

.quiz-type-badge {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 0.25rem 0.55rem;
  border-radius: 6px;
  margin-bottom: 1rem;
}

.quiz-prompt {
  font-size: 1.05rem;
  margin: 0 0 1.25rem;
  color: var(--ink-muted);
}

.quiz-prompt .han-large {
  display: block;
  font-family: var(--font-han);
  font-size: 2.5rem;
  font-weight: 500;
  color: var(--ink);
  margin: 0.25rem 0;
}

.quiz-prompt .en-large {
  display: block;
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--ink);
  margin: 0.25rem 0;
}

.quiz-body {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.option-btn {
  font: inherit;
  text-align: left;
  padding: 0.85rem 1rem;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg);
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}

.option-btn:hover:not(:disabled) {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.option-btn.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.option-btn.correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.option-btn.wrong {
  border-color: var(--error);
  background: var(--error-bg);
}

.option-btn:disabled {
  cursor: default;
}

.option-han {
  font-family: var(--font-han);
  font-size: 1.2rem;
}

.blank-sentence {
  font-size: 1.2rem;
  line-height: 1.8;
  font-family: var(--font-han);
}

.blank-sentence .blank {
  display: inline-block;
  min-width: 3rem;
  border-bottom: 2px solid var(--accent);
  color: var(--accent);
  font-weight: 600;
  text-align: center;
}

.order-zone {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  min-height: 3rem;
  padding: 0.75rem;
  border: 2px dashed var(--border);
  border-radius: var(--radius);
  margin-bottom: 1rem;
}

.order-zone.filled {
  border-style: solid;
  border-color: var(--accent-soft);
  background: var(--accent-soft);
}

.order-chip {
  font-family: var(--font-han);
  font-size: 1.1rem;
  padding: 0.45rem 0.85rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: transform 0.1s;
}

.order-chip:hover {
  border-color: var(--accent);
}

.order-chip.in-sentence {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.order-pool {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.quiz-feedback {
  margin: 1rem 0 0;
  padding: 0.75rem 1rem;
  border-radius: 8px;
  font-size: 0.95rem;
}

.quiz-feedback.correct {
  background: var(--success-bg);
  color: var(--success);
}

.quiz-feedback.wrong {
  background: var(--error-bg);
  color: var(--error);
}

.quiz-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1rem;
}

.quiz-empty,
.results-panel {
  text-align: center;
  padding: 2.5rem 1rem;
  background: var(--bg-card);
  border: 1px dashed var(--border);
  border-radius: var(--radius-lg);
  color: var(--ink-muted);
}

.results-panel h3 {
  margin: 0 0 0.5rem;
  color: var(--ink);
}

.results-score {
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent);
  margin: 0 0 1rem;
}

.results-breakdown {
  list-style: none;
  padding: 0;
  margin: 0 0 1.5rem;
  text-align: left;
  max-width: 400px;
  margin-inline: auto;
}

.results-breakdown li {
  padding: 0.35rem 0;
  font-size: 0.9rem;
}

.results-breakdown .ok {
  color: var(--success);
}

.results-breakdown .fail {
  color: var(--error);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 1.5rem 0;
  margin-top: auto;
}

.site-footer p {
  margin: 0;
  font-size: 0.85rem;
  color: var(--ink-muted);
  text-align: center;
}

@media (max-width: 600px) {
  .header-inner {
    flex-wrap: wrap;
  }

  .main-nav {
    order: 3;
    width: 100%;
    justify-content: center;
  }

  .header-stats {
    margin-left: auto;
  }
}