:root {
  --bg: #f5f7fb;
  --bg-2: #eef4ff;
  --card: rgba(255,255,255,.86);
  --card-solid: #ffffff;
  --ink: #111827;
  --muted: #64748b;
  --line: #e5e7eb;
  --accent: #2563eb;
  --accent-dark: #1e40af;
  --green: #10b981;
  --red: #ef4444;
  --yellow: #f59e0b;
  --purple: #8b5cf6;
  --shadow: 0 22px 60px rgba(15, 23, 42, .10);
  --radius: 24px;
  --sidebar: rgba(255,255,255,.78);
}
html[data-theme="dark"] {
  --bg: #08111f;
  --bg-2: #0f172a;
  --card: rgba(15,23,42,.78);
  --card-solid: #111827;
  --ink: #eef2ff;
  --muted: #94a3b8;
  --line: rgba(148,163,184,.22);
  --accent: #60a5fa;
  --accent-dark: #93c5fd;
  --sidebar: rgba(15,23,42,.86);
  --shadow: 0 22px 60px rgba(0,0,0,.28);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, rgba(37,99,235,.16), transparent 34%),
    radial-gradient(circle at 80% 20%, rgba(139,92,246,.12), transparent 30%),
    linear-gradient(135deg, var(--bg), var(--bg-2));
  min-height: 100vh;
}
button, input, select, textarea { font: inherit; }
button { color: inherit; }
.app { display: grid; grid-template-columns: 310px minmax(0, 1fr); min-height: 100vh; }
.sidebar {
  position: sticky; top: 0; height: 100vh; overflow: auto;
  padding: 22px;
  background: var(--sidebar);
  backdrop-filter: blur(18px);
  border-right: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 13px; margin-bottom: 24px; }
.brand-mark {
  width: 52px; height: 52px; display: grid; place-items: center;
  border-radius: 18px;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  color: #fff; font-weight: 900;
  box-shadow: 0 14px 30px rgba(37,99,235,.25);
}
.brand h1 { margin: 0; font-size: 1.08rem; }
.brand p { margin: 2px 0 0; color: var(--muted); font-size: .88rem; }
.main-nav { display: grid; gap: 8px; }
.nav-item {
  width: 100%;
  border: 1px solid transparent;
  background: transparent;
  padding: 12px 14px;
  border-radius: 15px;
  text-align: left;
  cursor: pointer;
  color: var(--muted);
  font-weight: 750;
}
.nav-item:hover, .nav-item.active {
  color: var(--ink);
  background: var(--card-solid);
  border-color: var(--line);
  box-shadow: 0 10px 24px rgba(15,23,42,.06);
}
.sidebar-card {
  margin-top: 18px;
  padding: 16px;
  border-radius: 20px;
  background: linear-gradient(135deg, rgba(37,99,235,.12), rgba(139,92,246,.10));
  border: 1px solid var(--line);
}
.tiny-label {
  margin: 0 0 7px;
  font-size: .72rem;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 900;
}
.ring-wrap { display: flex; align-items: center; gap: 12px; }
.ring {
  width: 70px; height: 70px;
  border-radius: 50%;
  display: grid; place-items: center;
  font-weight: 900;
  background: conic-gradient(var(--accent) 0deg, var(--line) 0deg);
}
.ring-wrap span { display: block; color: var(--muted); font-size: .83rem; margin-top: 3px; }
.sidebar-actions { display: grid; grid-template-columns: 1fr; gap: 8px; margin-top: 14px; }
.mini-btn, .primary, .secondary, .import-label {
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 11px 14px;
  cursor: pointer;
  font-weight: 800;
  background: var(--card-solid);
  box-shadow: 0 8px 18px rgba(15,23,42,.05);
}
.primary { background: var(--accent); color: #fff; border-color: var(--accent); }
.secondary { background: var(--card-solid); color: var(--ink); }
.danger { color: var(--red); }
.content {
  width: min(1280px, 100%);
  margin: 0 auto;
  padding: 28px;
}
.hero-card {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 22px;
  align-items: stretch;
  padding: clamp(22px, 4vw, 34px);
  border-radius: 30px;
  background: var(--card);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  backdrop-filter: blur(18px);
  overflow: hidden;
  position: relative;
}
.hero-card::after {
  content: "";
  position: absolute;
  inset: auto -80px -120px auto;
  width: 300px; height: 300px;
  background: radial-gradient(circle, rgba(37,99,235,.18), transparent 70%);
}
.hero-card h2 {
  position: relative;
  margin: 0;
  font-size: clamp(2.1rem, 5vw, 5rem);
  line-height: .92;
  letter-spacing: -0.06em;
  max-width: 880px;
}
.hero-copy { color: var(--muted); max-width: 780px; font-size: 1.04rem; line-height: 1.7; }
.hero-actions { display: flex; gap: 10px; flex-wrap: wrap; }
.quick-stats {
  position: relative;
  display: grid;
  grid-template-columns: repeat(2, 145px);
  gap: 12px;
}
.quick-stats div {
  padding: 18px;
  border-radius: 22px;
  background: var(--card-solid);
  border: 1px solid var(--line);
}
.quick-stats strong { display: block; font-size: 2.2rem; line-height: 1; }
.quick-stats span { display: block; color: var(--muted); margin-top: 7px; font-weight: 700; }
.view { display: none; margin-top: 22px; }
.view.active { display: block; animation: rise .22s ease; }
@keyframes rise { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
.section-head {
  display: flex; align-items: center; justify-content: space-between;
  gap: 14px; margin: 28px 0 16px;
}
.section-head h3 { margin: 0; font-size: clamp(1.6rem, 3vw, 2.2rem); letter-spacing: -.04em; }
.filter-row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
input, select, textarea {
  width: auto;
  min-width: 190px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--card-solid);
  color: var(--ink);
  padding: 11px 13px;
  outline: none;
}
input:focus, select:focus, textarea:focus { border-color: var(--accent); box-shadow: 0 0 0 4px rgba(37,99,235,.12); }
.panel, .chapter-progress-card, .lesson-card, .glossary-card, .question-card, .written-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: 0 14px 36px rgba(15,23,42,.07);
  backdrop-filter: blur(18px);
}
.dashboard-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
}
.chapter-progress-card { padding: 18px; position: relative; overflow: hidden; }
.chapter-progress-card h4 { margin: 0 0 8px; font-size: 1.05rem; }
.chapter-progress-card p { color: var(--muted); line-height: 1.5; min-height: 46px; }
.badges { display: flex; gap: 7px; flex-wrap: wrap; margin: 12px 0; }
.badge {
  display: inline-flex; align-items: center;
  padding: 6px 9px; border-radius: 999px;
  background: rgba(37,99,235,.10);
  color: var(--accent-dark);
  border: 1px solid var(--line);
  font-size: .78rem; font-weight: 850;
}
.progress-bar {
  height: 10px; background: var(--line); border-radius: 999px; overflow: hidden; margin-top: 12px;
}
.progress-bar span { display: block; height: 100%; width: 0; border-radius: inherit; background: var(--accent); }
.two-col { display: grid; grid-template-columns: 1.2fr .8fr; gap: 16px; margin-top: 16px; }
.panel { padding: 20px; }
.panel h4 { margin: 0 0 12px; font-size: 1.15rem; }
.path-list { margin: 0; padding-left: 20px; line-height: 1.8; color: var(--muted); }
.weak-item { display: flex; justify-content: space-between; gap: 10px; padding: 10px 0; border-bottom: 1px solid var(--line); }
.weak-item:last-child { border-bottom: 0; }
.lesson-list { display: grid; gap: 14px; }
.lesson-card { overflow: hidden; }
.lesson-top {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 14px;
  padding: 18px;
  border-bottom: 1px solid var(--line);
}
.lesson-title h4 { margin: 0; font-size: 1.2rem; }
.lesson-title p { margin: 6px 0 0; color: var(--muted); }
.lesson-body { display: grid; grid-template-columns: 1.25fr .75fr; gap: 16px; padding: 18px; }
.lesson-body ul { margin: 0; padding-left: 20px; line-height: 1.65; }
.lesson-body li::marker { color: var(--accent); }
.lesson-side { border-left: 1px solid var(--line); padding-left: 16px; }
.lesson-actions { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.icon-check {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 9px 11px; border: 1px solid var(--line); border-radius: 12px; cursor: pointer; background: var(--card-solid);
  font-weight: 800;
}
.icon-check input { min-width: 0; }
.memory-box {
  margin-top: 12px; padding: 13px; border-radius: 16px;
  background: rgba(16,185,129,.10); border: 1px solid rgba(16,185,129,.25);
}
.term-list { display: flex; flex-wrap: wrap; gap: 8px; }
.term-pill, .chapter-tag {
  display: inline-flex;
  padding: 7px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--card-solid);
  color: var(--muted);
  font-weight: 800;
  font-size: .82rem;
}
.glossary-grid {
  display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px;
}
.glossary-card { padding: 16px; }
.glossary-card h4 { margin: 0 0 8px; }
.glossary-card p { margin: 0; color: var(--muted); line-height: 1.55; }
.flash-layout {
  display: grid; grid-template-columns: minmax(0, 1fr) 230px; gap: 16px; align-items: stretch;
}
.flashcard {
  min-height: 410px; position: relative; transform-style: preserve-3d;
  transition: transform .35s ease; cursor: pointer; outline: none;
}
.flashcard.flipped { transform: rotateY(180deg); }
.card-face {
  position: absolute; inset: 0; backface-visibility: hidden;
  display: grid; place-content: center; text-align: center;
  border-radius: 30px;
  border: 1px solid var(--line);
  padding: 28px;
  background: linear-gradient(135deg, rgba(37,99,235,.95), rgba(139,92,246,.94));
  color: #fff;
  box-shadow: var(--shadow);
}
.card-face h4 { font-size: clamp(2.3rem, 7vw, 5rem); margin: 10px 0; line-height: .96; letter-spacing: -.07em; }
.card-face span { color: rgba(255,255,255,.78); font-weight: 800; }
.card-face.back {
  transform: rotateY(180deg);
  background: linear-gradient(135deg, rgba(15,23,42,.96), rgba(30,64,175,.95));
}
.card-face.back p:last-child { font-size: clamp(1.2rem, 2.6vw, 2rem); line-height: 1.55; max-width: 760px; }
.flash-side { display: grid; gap: 10px; align-content: start; }
.flash-side .primary, .flash-side .secondary { width: 100%; }
.muted { color: var(--muted); }
.question-card { padding: 16px; margin-bottom: 12px; }
.question-card h4 { margin: 0 0 10px; font-size: 1.06rem; line-height: 1.45; }
.question-meta { display: flex; flex-wrap: wrap; gap: 7px; margin-bottom: 12px; }
.option-btn {
  display: block; width: 100%;
  text-align: left;
  margin: 8px 0;
  padding: 12px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: var(--card-solid);
  cursor: pointer;
}
.option-btn:hover { border-color: var(--accent); }
.option-btn.correct { background: rgba(16,185,129,.14); border-color: rgba(16,185,129,.45); }
.option-btn.wrong { background: rgba(239,68,68,.14); border-color: rgba(239,68,68,.45); }
.explain { display: none; margin-top: 10px; color: var(--muted); line-height: 1.6; }
.practice-controls {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 12px;
  align-items: end;
  margin-bottom: 16px;
}
.practice-controls label { display: block; color: var(--muted); font-size: .82rem; font-weight: 800; margin-bottom: 5px; }
.practice-controls input, .practice-controls select { width: 100%; min-width: 0; }
.check-toggle {
  display: flex !important; align-items: center; gap: 8px;
  padding-bottom: 11px; color: var(--ink) !important; font-size: .9rem !important;
}
.check-toggle input { width: auto; min-width: 0; }
.results-card {
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(135deg, rgba(37,99,235,.12), rgba(16,185,129,.10));
  margin-bottom: 14px;
}
.results-card h4 { margin: 0 0 6px; font-size: 1.35rem; }
.timer-box {
  font-size: 1.3rem;
  font-weight: 900;
  padding: 12px 16px;
  border-radius: 16px;
  border: 1px solid var(--line);
  background: var(--card-solid);
}
.written-card { padding: 16px; margin-bottom: 12px; }
.written-card textarea, #notesArea {
  width: 100%; min-height: 130px; resize: vertical; margin-top: 10px;
}
.answer-box {
  display: none;
  padding: 13px;
  background: rgba(37,99,235,.08);
  border: 1px solid var(--line);
  border-radius: 16px;
  margin-top: 10px;
  line-height: 1.6;
}
.notes-actions { display: flex; gap: 12px; align-items: center; margin-top: 12px; }
.import-label { display: inline-flex; align-items: center; gap: 8px; }
.import-label input { display: none; }
#toast {
  position: fixed; z-index: 80; right: 18px; bottom: 18px;
  max-width: 340px; opacity: 0; pointer-events: none;
  padding: 13px 15px; border-radius: 16px;
  background: var(--ink); color: var(--bg);
  box-shadow: var(--shadow);
  transform: translateY(10px);
  transition: .22s ease;
}
#toast.show { opacity: 1; transform: none; }
.mobile-topbar { display: none; }
.close-menu { display: none; }
.icon-btn {
  width: 44px; height: 44px; border-radius: 14px; border: 1px solid var(--line);
  background: var(--card-solid); cursor: pointer;
}
@media (max-width: 1120px) {
  .dashboard-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .glossary-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .hero-card { grid-template-columns: 1fr; }
  .quick-stats { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .practice-controls { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 860px) {
  body { padding-top: 70px; }
  .mobile-topbar {
    display: flex;
    align-items: center; justify-content: space-between;
    position: fixed; z-index: 60; top: 0; left: 0; right: 0;
    padding: 10px 14px;
    background: var(--sidebar);
    backdrop-filter: blur(18px);
    border-bottom: 1px solid var(--line);
  }
  .mobile-topbar span { display: block; color: var(--muted); font-size: .8rem; }
  .app { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed; z-index: 70; inset: 0 auto 0 0; width: min(330px, 90vw);
    transform: translateX(-110%);
    transition: transform .25s ease;
  }
  .sidebar.open { transform: none; }
  .close-menu {
    display: block; position: absolute; top: 16px; right: 16px;
    border: 0; background: transparent; font-size: 2rem; cursor: pointer; color: var(--muted);
  }
  .content { padding: 16px; }
  .section-head { flex-direction: column; align-items: stretch; }
  .filter-row { width: 100%; }
  .filter-row input, .filter-row select { flex: 1 1 100%; width: 100%; }
  .lesson-body { grid-template-columns: 1fr; }
  .lesson-side { border-left: 0; padding-left: 0; border-top: 1px solid var(--line); padding-top: 14px; }
  .flash-layout { grid-template-columns: 1fr; }
  .flash-side { grid-template-columns: repeat(2, 1fr); }
  .two-col { grid-template-columns: 1fr; }
}
@media (max-width: 560px) {
  .quick-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .dashboard-grid, .glossary-grid { grid-template-columns: 1fr; }
  .practice-controls { grid-template-columns: 1fr; }
  .hero-actions .primary, .hero-actions .secondary { width: 100%; }
  .lesson-top { grid-template-columns: 1fr; }
  .flashcard { min-height: 330px; }
}
@media print {
  .sidebar, .mobile-topbar, .hero-actions, .filter-row, .lesson-actions, .flash-side, .practice-controls, #toast { display: none !important; }
  body { background: white; padding: 0; }
  .app { display: block; }
  .content { max-width: none; width: 100%; padding: 0; }
  .view { display: block !important; page-break-before: always; }
  .hero-card, .panel, .lesson-card, .question-card, .glossary-card { box-shadow: none; break-inside: avoid; }
}