:root {
  --bg: #0a0c14;
  --bg-soft: #111526;
  --card: #161b2e;
  --card-hover: #1d2440;
  --border: #2a3258;
  --text: #e8ebf7;
  --muted: #9099bd;
  --accent: #8b5cf6;
  --accent2: #22d3ee;
  --accent3: #f472b6;
  --good: #34d399;
  --bad: #f87171;
  --warn: #fbbf24;
  --radius: 14px;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: radial-gradient(900px 600px at 20% -10%, rgba(139,92,246,.20), transparent 60%),
              radial-gradient(700px 600px at 88% 10%, rgba(34,211,238,.12), transparent 55%),
              var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent2); text-decoration: none; }
a:hover { text-decoration: underline; }

.wrap { max-width: 1100px; margin: 0 auto; padding: 0 24px; }

/* Top bar (consistent with home.html nav-top) */
.topbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 32px;
  background: linear-gradient(180deg, rgba(13,17,23,.92), rgba(13,17,23,.72));
  backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid rgba(255,255,255,.06);
}
.topbar .logo {
  display: flex; align-items: center; gap: 10px;
  font-weight: 700; font-size: 15px; text-decoration: none;
  background: linear-gradient(90deg, #fff, #b9a8ff 60%, #7ee7d6);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.topbar .logo::before {
  content: "📚";
  display: grid; place-items: center;
  width: 30px; height: 30px; border-radius: 9px;
  background: rgba(124,92,255,.18);
  border: 1px solid rgba(124,92,255,.3);
  -webkit-text-fill-color: initial;
}
.topbar nav { display: flex; gap: 10px; align-items: center; }
.topbar nav a, .topbar nav button.logout {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 7px 14px;
  background: rgba(255,255,255,.04);
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 999px;
  color: #c2cad6; font-size: 13px; font-weight: 500; text-decoration: none;
  cursor: pointer; font-family: inherit;
  transition: background .15s, border-color .15s, color .15s, transform .1s;
}
.topbar nav a:hover, .topbar nav button.logout:hover {
  background: rgba(124,92,255,.14); border-color: rgba(124,92,255,.4);
  color: #fff; text-decoration: none;
}
.topbar nav a:active, .topbar nav button.logout:active { transform: translateY(1px); }
.topbar nav button.logout:hover {
  background: rgba(239,83,80,.12); border-color: rgba(239,83,80,.4); color: #ff8a85;
}
.topbar nav .user {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 6px 14px 6px 6px;
  background: rgba(255,255,255,.04);
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 999px;
  color: #e6edf3; font-size: 13px; font-weight: 500;
}
.topbar nav .user::before {
  content: attr(data-initial);
  width: 26px; height: 26px; border-radius: 50%;
  background: linear-gradient(135deg, #7c5cff, #19c3a6);
  display: grid; place-items: center;
  font-size: 12px; font-weight: 700; color: #fff;
  text-transform: uppercase;
}

/* Push content below fixed topbar */
body:has(.topbar) .wrap, body:has(.topbar) .quiz-page { padding-top: 24px; }
body:has(.topbar) { padding-top: 56px; }

@media (max-width: 640px) {
  .topbar { padding: 10px 16px; }
  .topbar nav a, .topbar nav button.logout { padding: 7px 11px; }
}

/* Auth (login/register) */
.auth-page {
  display: flex; align-items: center; justify-content: center;
  min-height: 100vh; padding: 24px;
}
.auth-card {
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 36px 32px; width: 100%; max-width: 420px;
  box-shadow: 0 30px 80px rgba(0,0,0,.4);
}
.auth-card h1 {
  font-size: 26px; font-weight: 800; margin-bottom: 8px;
  background: linear-gradient(120deg, #fff, #cbbcff 55%, #7be7ff);
  -webkit-background-clip: text; background-clip: text; -webkit-text-fill-color: transparent;
}
.auth-card p.sub { color: var(--muted); font-size: 14px; margin-bottom: 24px; }
.field { margin-bottom: 16px; }
.field label { display: block; font-size: 13px; color: var(--muted); margin-bottom: 6px; }
.field input {
  width: 100%; padding: 11px 14px; background: var(--bg-soft); border: 1px solid var(--border);
  border-radius: 10px; color: var(--text); font-size: 15px;
  font-family: inherit; outline: none; transition: border-color .15s;
}
.field input:focus { border-color: var(--accent); }
.btn {
  display: inline-block; padding: 11px 20px; border-radius: 10px; border: none;
  font-size: 15px; font-weight: 600; cursor: pointer;
  font-family: inherit; transition: transform .1s, opacity .15s;
}
.btn:active { transform: translateY(1px); }
.btn-primary {
  background: linear-gradient(120deg, var(--accent), var(--accent2));
  color: #0a0c14; width: 100%;
}
.btn-primary:hover { opacity: .9; }
.btn-ghost {
  background: transparent; border: 1px solid var(--border); color: var(--text);
}
.btn-ghost:hover { border-color: var(--accent); }
.toggle { text-align: center; margin-top: 18px; color: var(--muted); font-size: 14px; }
.toggle a { cursor: pointer; }
.alert { padding: 10px 14px; border-radius: 8px; font-size: 14px; margin-bottom: 16px; }
.alert.error { background: rgba(248,113,113,.12); color: #f87171; border: 1px solid rgba(248,113,113,.3); }
.alert.success { background: rgba(52,211,153,.12); color: var(--good); border: 1px solid rgba(52,211,153,.3); }

/* Dashboard */
.hero-mini { padding: 48px 24px 24px; }
.hero-mini h1 {
  font-size: clamp(28px, 4vw, 42px); font-weight: 800; letter-spacing: -.5px;
  background: linear-gradient(120deg, #fff, #cbbcff 55%, #7be7ff);
  -webkit-background-clip: text; background-clip: text; -webkit-text-fill-color: transparent;
}
.hero-mini p { color: var(--muted); margin-top: 8px; }

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 16px; padding: 24px; }
.card {
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px 22px 18px; transition: border-color .15s, transform .15s;
}
.card:hover { border-color: var(--accent); transform: translateY(-2px); }
.card .title { font-size: 17px; font-weight: 700; margin-bottom: 4px; }
.card .desc { color: var(--muted); font-size: 13px; margin-bottom: 14px; }
.card .meta {
  display: flex; gap: 16px; font-size: 12px; color: var(--muted); margin-bottom: 14px;
}
.card .meta b { color: var(--accent2); }
.card .actions { display: flex; gap: 8px; }
.card .actions a {
  flex: 1; padding: 8px 12px; border-radius: 8px; text-align: center;
  font-size: 13px; font-weight: 600; transition: opacity .15s;
}
.card .actions .btn-tut {
  background: rgba(52,211,153,.12); color: var(--good); border: 1px solid rgba(52,211,153,.3);
}
.card .actions .btn-tut:hover { text-decoration: none; opacity: .8; }
.card .actions .btn-quiz {
  background: rgba(139,92,246,.15); color: #c4b5fd; border: 1px solid rgba(139,92,246,.3);
}
.card .actions .btn-quiz:hover { text-decoration: none; opacity: .8; }

/* Quiz page */
.quiz-page { padding: 24px; max-width: 820px; margin: 0 auto; }
.quiz-page h1 { font-size: 26px; margin-bottom: 8px; }
.progress {
  background: var(--card); border: 1px solid var(--border); border-radius: 999px;
  height: 8px; overflow: hidden; margin: 16px 0 22px;
}
.progress > div { height: 100%; background: linear-gradient(120deg, var(--accent), var(--accent2)); transition: width .3s; }
.q-card {
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 24px; margin-bottom: 16px;
}
.q-card .qnum { color: var(--muted); font-size: 13px; margin-bottom: 8px; }
.q-card .question { font-size: 17px; font-weight: 600; margin-bottom: 16px; line-height: 1.5; }
.options { display: flex; flex-direction: column; gap: 10px; }
.option {
  background: var(--bg-soft); border: 1px solid var(--border); border-radius: 10px;
  padding: 12px 16px; cursor: pointer; transition: border-color .15s, background .15s;
  display: flex; align-items: center; gap: 12px;
}
.option:hover { border-color: var(--accent); }
.option.selected { border-color: var(--accent); background: rgba(139,92,246,.08); }
.option.correct { border-color: var(--good); background: rgba(52,211,153,.08); }
.option.wrong { border-color: var(--bad); background: rgba(248,113,113,.08); }
.option .letter {
  display: inline-block; width: 26px; height: 26px; border-radius: 50%;
  background: var(--bg); border: 1px solid var(--border);
  font-weight: 700; font-size: 13px; text-align: center; line-height: 24px;
  flex-shrink: 0;
}
.option.selected .letter { background: var(--accent); color: var(--bg); border-color: var(--accent); }
.option.correct .letter { background: var(--good); color: var(--bg); border-color: var(--good); }
.option.wrong .letter { background: var(--bad); color: var(--bg); border-color: var(--bad); }
.explain {
  margin-top: 14px; padding: 12px 14px; border-radius: 8px;
  background: rgba(34,211,238,.06); border-left: 3px solid var(--accent2);
  color: var(--muted); font-size: 13px;
}
.explain b { color: var(--accent2); }
.explain.correct { background: rgba(52,211,153,.06); border-left-color: var(--good); }
.explain.correct b { color: var(--good); }
.explain.wrong { background: rgba(248,113,113,.06); border-left-color: var(--bad); }
.explain.wrong b { color: var(--bad); }

.score-banner {
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 32px; text-align: center; margin-bottom: 24px;
}
.score-banner .emoji { font-size: 42px; margin-bottom: 12px; }
.score-banner h2 {
  font-size: 38px; font-weight: 800; margin-bottom: 8px;
  background: linear-gradient(120deg, #fff, #cbbcff 55%, #7be7ff);
  -webkit-background-clip: text; background-clip: text; -webkit-text-fill-color: transparent;
}
.score-banner p { color: var(--muted); }
.btn-row { display: flex; gap: 12px; justify-content: center; margin-top: 24px; }

/* History */
.attempts table {
  width: 100%; border-collapse: collapse; background: var(--card);
  border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden;
}
.attempts th, .attempts td { padding: 12px 16px; text-align: left; border-bottom: 1px solid var(--border); }
.attempts th { background: var(--bg-soft); font-size: 13px; color: var(--muted); font-weight: 600; }
.attempts td { font-size: 14px; }
.attempts tr:last-child td { border-bottom: none; }
.attempts tr:hover td { background: var(--card-hover); }
.score-pill {
  display: inline-block; padding: 3px 10px; border-radius: 999px; font-size: 12px; font-weight: 600;
}
.score-pill.high { background: rgba(52,211,153,.15); color: var(--good); }
.score-pill.mid  { background: rgba(251,191,36,.15); color: var(--warn); }
.score-pill.low  { background: rgba(248,113,113,.15); color: var(--bad); }

.empty { text-align: center; padding: 60px 20px; color: var(--muted); }
.spinner {
  display: inline-block; width: 16px; height: 16px;
  border: 2px solid rgba(255,255,255,.2); border-top-color: var(--accent);
  border-radius: 50%; animation: spin .6s linear infinite; vertical-align: middle;
}
@keyframes spin { to { transform: rotate(360deg); } }

@media (max-width: 600px) {
  .grid { grid-template-columns: 1fr; }
  .hero-mini { padding: 32px 18px 16px; }
}