:root {
  --bg: #f6f7fb;
  --panel: #ffffff;
  --ink: #1a1f36;
  --muted: #667085;
  --border: #e4e7ec;
  --accent: #4f46e5;
  --accent-ink: #ffffff;
  --correct: #067647;
  --correct-bg: #ecfdf3;
  --incorrect: #b42318;
  --incorrect-bg: #fef3f2;
  --warn-bg: #fffaeb;
  --warn-border: #fedf89;
  --radius: 14px;
  font-family: "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto, Helvetica, Arial, sans-serif;
  color-scheme: light;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  min-height: 100vh;
}

body {
  display: flex;
  flex-direction: column;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

img, svg { max-width: 100%; }

/* ---------- Topbar ---------- */
.topbar {
  background: var(--panel);
  border-bottom: 1px solid var(--border);
  padding: 12px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  position: sticky;
  top: 0;
  z-index: 20;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.15rem;
  letter-spacing: -0.01em;
  color: var(--ink);
  text-decoration: none;
}

.brand .logo-dot {
  width: 30px;
  height: 30px;
  border-radius: 9px;
  background: linear-gradient(135deg, #4f46e5, #7c3aed);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 1rem;
}

.topbar-right {
  display: flex;
  align-items: center;
  gap: 14px;
  font-size: 0.85rem;
  color: var(--muted);
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--ink);
  padding: 9px 16px;
  border-radius: 10px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  font-family: inherit;
}
.btn:hover { border-color: var(--accent); text-decoration: none; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}
.btn-primary:hover { filter: brightness(1.08); }

.btn-ghost {
  border-color: transparent;
  background: transparent;
}
.btn-ghost:hover { background: var(--bg); }

/* ---------- Layout ---------- */
.page {
  flex: 1;
  width: 100%;
  max-width: 1180px;
  margin: 0 auto;
  padding: 32px 24px 64px;
}

.footer {
  text-align: center;
  padding: 18px;
  font-size: 0.8rem;
  color: var(--muted);
  border-top: 1px solid var(--border);
  background: var(--panel);
}

/* ---------- Cards / progress (landing) ---------- */
.hero {
  margin-bottom: 32px;
}
.hero h1 {
  font-size: 1.9rem;
  margin: 0 0 8px;
  letter-spacing: -0.02em;
}
.hero p {
  color: var(--muted);
  font-size: 1.02rem;
  max-width: 640px;
  margin: 0;
}

.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 20px;
}

.course-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  border-top: 4px solid var(--course-color, var(--accent));
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.course-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(20, 20, 43, 0.08);
}

.course-card-head {
  display: flex;
  align-items: center;
  gap: 12px;
}

.course-icon {
  width: 44px;
  height: 44px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  background: color-mix(in srgb, var(--course-color, var(--accent)) 15%, white);
}

.course-card h3 {
  margin: 0;
  font-size: 1.1rem;
}
.course-card .exam-code {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--course-color, var(--accent));
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.course-card p.desc {
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.5;
  flex: 1;
}

.progress-bar-track {
  height: 8px;
  background: var(--bg);
  border-radius: 999px;
  overflow: hidden;
  border: 1px solid var(--border);
}
.progress-bar-fill {
  height: 100%;
  background: var(--course-color, var(--accent));
  border-radius: 999px;
  transition: width 0.3s ease;
}
.progress-label {
  font-size: 0.78rem;
  color: var(--muted);
  display: flex;
  justify-content: space-between;
}

.course-card-footer {
  display: flex;
  gap: 8px;
  align-items: center;
  justify-content: space-between;
}

.badge {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 3px 9px;
  border-radius: 999px;
  background: var(--correct-bg);
  color: var(--correct);
}
.badge.muted { background: var(--bg); color: var(--muted); }

/* ---------- Course layout (sidebar + content) ---------- */
.course-layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 28px;
  align-items: start;
}

@media (max-width: 860px) {
  .course-layout { grid-template-columns: 1fr; }
}

.sidebar {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  position: sticky;
  top: 76px;
}

.sidebar-title {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
  font-weight: 700;
  margin: 0 0 10px;
}

.chapter-list {
  list-style: none;
  margin: 0 0 16px;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.chapter-list a {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 10px;
  border-radius: 9px;
  color: var(--ink);
  font-size: 0.88rem;
  text-decoration: none;
}
.chapter-list a:hover { background: var(--bg); }
.chapter-list a.active {
  background: color-mix(in srgb, var(--course-color, var(--accent)) 12%, white);
  color: var(--course-color, var(--accent));
  font-weight: 700;
}

.chapter-num {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  border: 1.5px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.72rem;
  flex-shrink: 0;
  color: var(--muted);
}
.chapter-list a.active .chapter-num {
  border-color: var(--course-color, var(--accent));
  color: var(--course-color, var(--accent));
}
.chapter-list a.done .chapter-num {
  background: var(--correct);
  border-color: var(--correct);
  color: #fff;
}

.exam-cta {
  border-top: 1px solid var(--border);
  padding-top: 14px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.exam-cta .btn { justify-content: center; width: 100%; }

/* ---------- Chapter content ---------- */
.content-panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px;
}

@media (max-width: 600px) {
  .content-panel { padding: 22px; }
}

.chapter-eyebrow {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--course-color, var(--accent));
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 6px;
}

.content-panel h1 {
  margin: 0 0 6px;
  font-size: 1.7rem;
  letter-spacing: -0.02em;
}

.chapter-summary {
  color: var(--muted);
  font-size: 1rem;
  margin: 0 0 28px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}

.content-panel h2 {
  font-size: 1.25rem;
  margin: 32px 0 12px;
  letter-spacing: -0.01em;
}
.content-panel h2:first-child { margin-top: 0; }

.content-panel p {
  line-height: 1.7;
  font-size: 0.98rem;
  margin: 0 0 14px;
}

.content-panel ul, .content-panel ol {
  line-height: 1.7;
  font-size: 0.98rem;
  margin: 0 0 14px;
  padding-left: 22px;
}
.content-panel li { margin-bottom: 6px; }

.content-panel strong { color: var(--ink); }
.content-panel code {
  background: var(--bg);
  border: 1px solid var(--border);
  padding: 1px 6px;
  border-radius: 5px;
  font-size: 0.88em;
}

.callout {
  background: var(--warn-bg);
  border: 1px solid var(--warn-border);
  border-radius: 10px;
  padding: 14px 16px;
  margin: 0 0 18px;
  font-size: 0.92rem;
  line-height: 1.6;
}
.callout strong { display: block; margin-bottom: 4px; }

.table-wrap { overflow-x: auto; margin: 0 0 18px; }
table.study-table {
  border-collapse: collapse;
  width: 100%;
  font-size: 0.9rem;
}
table.study-table th, table.study-table td {
  border: 1px solid var(--border);
  padding: 8px 12px;
  text-align: left;
}
table.study-table th {
  background: var(--bg);
  font-weight: 700;
}

/* ---------- Quiz ---------- */
.quiz-block {
  margin-top: 36px;
  padding-top: 28px;
  border-top: 2px dashed var(--border);
}
.quiz-block h2 { margin-top: 0; }

.quiz-question {
  margin-bottom: 22px;
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 12px;
}
.quiz-question p.q-text {
  font-weight: 600;
  margin: 0 0 12px;
  font-size: 0.95rem;
}
.q-options {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.q-option {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 9px;
  cursor: pointer;
  font-size: 0.9rem;
  line-height: 1.5;
}
.q-option:hover { border-color: var(--course-color, var(--accent)); }
.q-option input { margin-top: 3px; }
.q-option.correct { background: var(--correct-bg); border-color: var(--correct); }
.q-option.incorrect { background: var(--incorrect-bg); border-color: var(--incorrect); }

.q-explanation {
  margin-top: 10px;
  font-size: 0.86rem;
  color: var(--muted);
  background: var(--bg);
  padding: 10px 12px;
  border-radius: 8px;
  display: none;
}
.q-explanation.show { display: block; }

.quiz-result-banner {
  display: none;
  padding: 14px 18px;
  border-radius: 12px;
  margin-bottom: 20px;
  font-weight: 700;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}
.quiz-result-banner.show { display: flex; }
.quiz-result-banner.pass { background: var(--correct-bg); color: var(--correct); }
.quiz-result-banner.fail { background: var(--incorrect-bg); color: var(--incorrect); }

.chapter-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 32px;
  gap: 12px;
}

/* ---------- Exam ---------- */
.exam-shell {
  max-width: 820px;
  margin: 0 auto;
}

.exam-header-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 20px;
  margin-bottom: 20px;
  gap: 16px;
  flex-wrap: wrap;
}

.exam-timer {
  font-variant-numeric: tabular-nums;
  font-weight: 800;
  font-size: 1.1rem;
}
.exam-timer.low { color: var(--incorrect); }

.exam-progress-text { color: var(--muted); font-size: 0.88rem; }

.palette {
  display: grid;
  grid-template-columns: repeat(10, 1fr);
  gap: 6px;
  margin-bottom: 20px;
}
@media (max-width: 600px) {
  .palette { grid-template-columns: repeat(6, 1fr); }
}
.palette button {
  aspect-ratio: 1;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--panel);
  font-size: 0.78rem;
  cursor: pointer;
  color: var(--muted);
  font-family: inherit;
}
.palette button.current { border-color: var(--ink); border-width: 2px; color: var(--ink); font-weight: 800; }
.palette button.answered { background: color-mix(in srgb, var(--accent) 14%, white); color: var(--accent); border-color: var(--accent); }
.palette button.flagged::after { content: "•"; color: #f59e0b; font-size: 1.3rem; line-height: 0; position: relative; top: 6px; left: 3px; }

.exam-question-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 20px;
}

.exam-footer-nav {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  flex-wrap: wrap;
}
.exam-footer-nav .spacer-group { display: flex; gap: 10px; }

.exam-intro, .exam-result {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px;
  text-align: center;
}
.exam-intro h1, .exam-result h1 { margin-top: 0; }
.exam-intro ul {
  text-align: left;
  display: inline-block;
  line-height: 1.8;
  color: var(--muted);
}

.score-ring-wrap {
  display: flex;
  justify-content: center;
  margin: 24px 0;
}

.result-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 14px;
  margin: 24px 0;
  text-align: left;
}
.result-stat {
  background: var(--bg);
  border-radius: 10px;
  padding: 14px 16px;
}
.result-stat .num { font-size: 1.5rem; font-weight: 800; }
.result-stat .lbl { font-size: 0.78rem; color: var(--muted); }

.review-item {
  text-align: left;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 14px;
}
.review-item .tag {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: 999px;
  margin-bottom: 8px;
  display: inline-block;
}
.review-item.correct .tag { background: var(--correct-bg); color: var(--correct); }
.review-item.incorrect .tag { background: var(--incorrect-bg); color: var(--incorrect); }

.breadcrumb {
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 16px;
}
.breadcrumb a { color: var(--muted); }

.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--muted);
}