:root {
  --bg: #f0f4ff;
  --bg2: #ffffff;
  --bg3: #e8eeff;
  --surface: #ffffff;
  --surface2: #f8faff;
  --border: #d0d8ff;
  --text: #1a1f3a;
  --text2: #4a5280;
  --text3: #8892b8;
  --accent: #6c63ff;
  --accent2: #ff6584;
  --accent3: #43e97b;
  --accent4: #f7971e;
  --shadow: 0 4px 24px rgba(108,99,255,0.10);
  --shadow2: 0 8px 40px rgba(108,99,255,0.18);
  --radius: 18px;
  --radius-sm: 10px;
  --transition: 0.3s cubic-bezier(.4,0,.2,1);
}

[data-theme="dark"] {
  --bg: #0f1123;
  --bg2: #181c35;
  --bg3: #1e2340;
  --surface: #1e2340;
  --surface2: #252a4a;
  --border: #2e3460;
  --text: #e8eeff;
  --text2: #a0aacc;
  --text3: #5a6490;
  --shadow: 0 4px 24px rgba(0,0,0,0.35);
  --shadow2: 0 8px 40px rgba(0,0,0,0.5);
}

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

body {
  font-family: 'Inter', 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  transition: background var(--transition), color var(--transition);
}

/* NAV */
nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 2rem;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow);
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
}

.nav-logo img {
  height: 36px;
  width: auto;
  display: block;
  object-fit: contain;
}

.nav-right {
  display: flex;
  align-items: center;
  gap: 1rem;
}

/* XP BAR in nav */
.nav-xp {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--bg3);
  border-radius: 50px;
  padding: 0.35rem 0.9rem;
  border: 1px solid var(--border);
}

.nav-xp .level-badge {
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  font-weight: 800;
  font-size: 0.75rem;
  border-radius: 50px;
  padding: 0.18rem 0.6rem;
  letter-spacing: 0.5px;
}

.nav-xp .xp-label {
  font-size: 0.75rem;
  color: var(--text3);
  font-weight: 600;
}

.xp-bar-mini {
  width: 70px;
  height: 6px;
  background: var(--border);
  border-radius: 10px;
  overflow: hidden;
}

.xp-bar-mini-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  border-radius: 10px;
  transition: width 0.6s cubic-bezier(.4,0,.2,1);
}

/* DARK MODE TOGGLE */
.toggle-dark {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: 50px;
  padding: 0.4rem 1rem;
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text2);
  display: flex;
  align-items: center;
  gap: 0.4rem;
  transition: all var(--transition);
}

.toggle-dark:hover {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

/* HERO */
.hero {
  text-align: center;
  padding: 5rem 2rem 3rem;
  background: linear-gradient(135deg, var(--bg) 0%, var(--bg3) 100%);
}

.hero-badge {
  display: inline-block;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  font-weight: 700;
  font-size: 0.8rem;
  border-radius: 50px;
  padding: 0.3rem 1rem;
  margin-bottom: 1.2rem;
  letter-spacing: 1px;
  text-transform: uppercase;
}

.hero h1 {
  font-size: clamp(2.2rem, 5vw, 3.8rem);
  font-weight: 900;
  line-height: 1.15;
  letter-spacing: -1.5px;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, var(--text) 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.15rem;
  color: var(--text2);
  max-width: 520px;
  margin: 0 auto 2rem;
  line-height: 1.7;
}

/* SUBJECTS GRID */
.subjects-section {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem 2rem 5rem;
}

.section-title {
  font-size: 1.5rem;
  font-weight: 800;
  margin-bottom: 1.5rem;
  letter-spacing: -0.5px;
}

.subjects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
}

.subject-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2rem;
  text-decoration: none;
  color: var(--text);
  display: flex;
  flex-direction: column;
  gap: 1rem;
  box-shadow: var(--shadow);
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.subject-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--card-color1), var(--card-color2));
}

.subject-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow2);
  border-color: var(--accent);
}

.subject-card .icon {
  font-size: 2.5rem;
  width: 60px;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 14px;
  background: var(--bg3);
}

.subject-card h3 {
  font-size: 1.25rem;
  font-weight: 800;
}

.subject-card p {
  font-size: 0.9rem;
  color: var(--text2);
  line-height: 1.6;
}

.subject-card .card-meta {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: auto;
}

.card-tag {
  font-size: 0.75rem;
  font-weight: 700;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: 50px;
  padding: 0.2rem 0.7rem;
  color: var(--text3);
}

.card-arrow {
  margin-left: auto;
  font-size: 1.2rem;
  color: var(--text3);
  transition: transform var(--transition);
}

.subject-card:hover .card-arrow { transform: translateX(5px); color: var(--accent); }

/* LEVEL PANEL */
.level-panel {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 2rem 2rem;
}

.level-card {
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent2) 100%);
  border-radius: var(--radius);
  padding: 2rem;
  color: #fff;
  display: flex;
  align-items: center;
  gap: 2rem;
  flex-wrap: wrap;
  box-shadow: 0 8px 32px rgba(108,99,255,0.3);
}

.level-info h2 {
  font-size: 1.6rem;
  font-weight: 900;
  letter-spacing: -0.5px;
}

.level-info p {
  opacity: 0.85;
  font-size: 0.9rem;
  margin-top: 0.3rem;
}

.xp-section {
  flex: 1;
  min-width: 200px;
}

.xp-row {
  display: flex;
  justify-content: space-between;
  font-size: 0.82rem;
  opacity: 0.85;
  margin-bottom: 0.4rem;
  font-weight: 600;
}

.xp-bar-full {
  height: 12px;
  background: rgba(255,255,255,0.25);
  border-radius: 10px;
  overflow: hidden;
}

.xp-bar-full-fill {
  height: 100%;
  background: rgba(255,255,255,0.9);
  border-radius: 10px;
  transition: width 0.8s cubic-bezier(.4,0,.2,1);
}

.stats-row {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.stat-item {
  text-align: center;
}

.stat-item .val {
  font-size: 1.6rem;
  font-weight: 900;
  line-height: 1;
}

.stat-item .lbl {
  font-size: 0.72rem;
  opacity: 0.75;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-top: 0.2rem;
}

/* ========== QUIZ PAGE ========== */
.quiz-page {
  max-width: 860px;
  margin: 0 auto;
  padding: 2rem 1.5rem 5rem;
}

.quiz-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 2rem;
  flex-wrap: wrap;
}

.back-btn {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  text-decoration: none;
  color: var(--text2);
  font-weight: 600;
  font-size: 0.9rem;
  background: var(--surface);
  border: 1px solid var(--border);
  padding: 0.45rem 1rem;
  border-radius: 50px;
  transition: all var(--transition);
}

.back-btn:hover { color: var(--accent); border-color: var(--accent); }

.quiz-title-wrap { flex: 1; }
.quiz-title-wrap h1 {
  font-size: 1.8rem;
  font-weight: 900;
  letter-spacing: -0.5px;
}

.quiz-title-wrap p { color: var(--text2); font-size: 0.9rem; margin-top: 0.2rem; }

/* PROGRESS BAR */
.progress-wrap {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.2rem 1.5rem;
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  gap: 1.2rem;
}

.progress-bar-outer {
  flex: 1;
  height: 10px;
  background: var(--border);
  border-radius: 10px;
  overflow: hidden;
}

.progress-bar-inner {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  border-radius: 10px;
  transition: width 0.5s cubic-bezier(.4,0,.2,1);
}

.progress-text {
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text2);
  white-space: nowrap;
}

.score-chip {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: 50px;
  padding: 0.25rem 0.8rem;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--accent);
  white-space: nowrap;
}

/* STREAK */
.streak-bar {
  display: flex;
  gap: 0.4rem;
  margin-bottom: 1.2rem;
  align-items: center;
}

.streak-dot {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  transition: all 0.3s;
}

.streak-dot.correct { background: linear-gradient(135deg, #43e97b, #38f9d7); }
.streak-dot.wrong { background: linear-gradient(135deg, #ff6584, #ff8e53); }

/* FLASHCARD */
.flashcard-wrap {
  perspective: 1000px;
  margin-bottom: 1.5rem;
}

.flashcard {
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 3rem 2.5rem;
  text-align: center;
  box-shadow: var(--shadow2);
  min-height: 220px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.8rem;
  position: relative;
  transition: all var(--transition);
}

.card-number {
  position: absolute;
  top: 1rem; right: 1.2rem;
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text3);
  background: var(--bg3);
  border-radius: 50px;
  padding: 0.2rem 0.6rem;
}

.card-category {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--accent);
  background: rgba(108,99,255,0.1);
  border-radius: 50px;
  padding: 0.2rem 0.8rem;
}

.card-question {
  font-size: clamp(1.1rem, 3vw, 1.5rem);
  font-weight: 800;
  line-height: 1.4;
  letter-spacing: -0.3px;
}

/* ANSWERS */
.answers-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.9rem;
  margin-bottom: 1.5rem;
}

@media (max-width: 540px) {
  .answers-grid { grid-template-columns: 1fr; }
}

.answer-btn {
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1rem 1.2rem;
  text-align: left;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text);
  display: flex;
  align-items: flex-start;
  gap: 0.8rem;
  transition: all var(--transition);
  line-height: 1.5;
}

.answer-btn:hover:not(:disabled) {
  border-color: var(--accent);
  background: rgba(108,99,255,0.06);
  transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(108,99,255,0.12);
}

.answer-btn .letter {
  width: 26px;
  height: 26px;
  min-width: 26px;
  border-radius: 8px;
  background: var(--bg3);
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.78rem;
  font-weight: 800;
  color: var(--text2);
  transition: all var(--transition);
}

.answer-btn:hover:not(:disabled) .letter {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.answer-btn.correct {
  border-color: #43e97b;
  background: rgba(67,233,123,0.1);
}

.answer-btn.correct .letter {
  background: #43e97b;
  color: #fff;
  border-color: #43e97b;
}

.answer-btn.wrong {
  border-color: #ff6584;
  background: rgba(255,101,132,0.1);
}

.answer-btn.wrong .letter {
  background: #ff6584;
  color: #fff;
  border-color: #ff6584;
}

.answer-btn:disabled { cursor: not-allowed; }

/* FEEDBACK */
.feedback-box {
  border-radius: var(--radius-sm);
  padding: 1rem 1.4rem;
  margin-bottom: 1rem;
  font-weight: 600;
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  gap: 0.7rem;
  animation: slideUp 0.3s ease;
}

.feedback-box.correct {
  background: rgba(67,233,123,0.12);
  border: 1px solid rgba(67,233,123,0.4);
  color: #1a7a47;
}

[data-theme="dark"] .feedback-box.correct { color: #43e97b; }

.feedback-box.wrong {
  background: rgba(255,101,132,0.12);
  border: 1px solid rgba(255,101,132,0.4);
  color: #a0203a;
}

[data-theme="dark"] .feedback-box.wrong { color: #ff6584; }

.xp-gain {
  margin-left: auto;
  font-size: 0.8rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* NEXT BTN */
.next-btn {
  display: block;
  width: 100%;
  padding: 1rem;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 1rem;
  font-weight: 800;
  cursor: pointer;
  transition: all var(--transition);
  letter-spacing: 0.3px;
  box-shadow: 0 4px 20px rgba(108,99,255,0.3);
}

.next-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(108,99,255,0.4);
}

/* RESULTS */
.results-wrap {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 3rem 2rem;
  text-align: center;
  box-shadow: var(--shadow2);
}

.results-wrap .big-emoji { font-size: 4rem; margin-bottom: 1rem; }

.results-wrap h2 {
  font-size: 2rem;
  font-weight: 900;
  letter-spacing: -0.5px;
  margin-bottom: 0.5rem;
}

.results-wrap .subtitle {
  color: var(--text2);
  margin-bottom: 2rem;
  font-size: 0.95rem;
}

.results-stats {
  display: flex;
  justify-content: center;
  gap: 2rem;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.results-stat {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1rem 1.5rem;
  min-width: 120px;
}

.results-stat .num {
  font-size: 2rem;
  font-weight: 900;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.results-stat .lbl {
  font-size: 0.78rem;
  color: var(--text3);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-top: 0.3rem;
}

.level-up-banner {
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  border-radius: var(--radius-sm);
  padding: 1rem 1.5rem;
  margin-bottom: 1.5rem;
  font-weight: 800;
  font-size: 1.1rem;
  animation: pulse 1s ease infinite alternate;
  display: none;
}

.level-up-banner.show { display: block; }

@keyframes pulse {
  from { box-shadow: 0 4px 20px rgba(108,99,255,0.3); }
  to { box-shadow: 0 8px 40px rgba(108,99,255,0.6); }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* XP POPUP */
.xp-popup {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) scale(0.5);
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  border-radius: var(--radius);
  padding: 1.5rem 2.5rem;
  font-size: 1.4rem;
  font-weight: 900;
  text-align: center;
  z-index: 1000;
  pointer-events: none;
  opacity: 0;
  transition: all 0.5s cubic-bezier(.34,1.56,.64,1);
  box-shadow: 0 16px 60px rgba(108,99,255,0.5);
}

.xp-popup.show {
  opacity: 1;
  transform: translate(-50%, -50%) scale(1);
}

.xp-popup.hide {
  opacity: 0;
  transform: translate(-50%, -150%) scale(0.8);
}

.result-btns {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

.result-btns a, .result-btns button {
  padding: 0.85rem 1.8rem;
  border-radius: 50px;
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  text-decoration: none;
  transition: all var(--transition);
  border: 2px solid;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  border-color: transparent;
  box-shadow: 0 4px 20px rgba(108,99,255,0.3);
}

.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 8px 30px rgba(108,99,255,0.4); }

.btn-secondary {
  background: transparent;
  color: var(--text2);
  border-color: var(--border);
}

.btn-secondary:hover { border-color: var(--accent); color: var(--accent); }

/* RESPONSIVE */
@media (max-width: 640px) {
  nav { padding: 0.8rem 1rem; }
  .hero { padding: 3rem 1rem 2rem; }
  .subjects-section { padding: 1.5rem 1rem 3rem; }
  .level-panel { padding: 0 1rem 1.5rem; }
  .quiz-page { padding: 1.5rem 1rem 3rem; }
  .flashcard { padding: 2rem 1.2rem; }
  .level-card { gap: 1rem; }
}