/* NetLearner Design System v4
   Inspired by frontend-design skill principles:
   dark theme, monospace tech aesthetic, Cisco blue accent */

:root {
  --bg-primary: #0f1117;
  --bg-secondary: #181b24;
  --bg-card: #1e2231;
  --bg-hover: #262b3d;
  --bg-input: #181b24;

  --text-primary: #e4e7eb;
  --text-secondary: #9499a6;
  --text-muted: #5c6170;

  --blue: #4fc3f7;
  --green: #66bb6a;
  --red: #ef5350;
  --orange: #ffa726;

  --border: #2a2e3d;
  --radius: 10px;
  --radius-sm: 6px;

  --huawei-red: #e53935;
  --vendor-color: var(--blue);
}

[data-theme="light"] {
  --bg-primary: #f2f4f8;
  --bg-secondary: #ffffff;
  --bg-card: #ffffff;
  --bg-hover: #eef0f4;
  --bg-input: #ffffff;
  --text-primary: #1a1d27;
  --text-secondary: #5c6170;
  --text-muted: #9499a6;
  --border: #dce0e8;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
}
a { color: var(--blue); text-decoration: none; }

/* Navigation */
.nav {
  position: sticky; top: 0; z-index: 100;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center;
  padding: 0 20px; height: 52px;
}
.nav-brand {
  font-family: 'SF Mono', 'Cascadia Code', 'Consolas', monospace;
  font-size: 17px; font-weight: 700;
  color: var(--blue); margin-right: 24px;
}
.nav-links { display: flex; gap: 2px; }
.nav-link {
  padding: 6px 12px; border-radius: var(--radius-sm);
  font-size: 13px; font-weight: 500;
  color: var(--text-secondary); cursor: pointer;
  transition: 0.12s;
}
.nav-link:hover { background: var(--bg-hover); color: var(--text-primary); }
.nav-link.active { color: var(--blue); background: rgba(79,195,247,0.08); }

/* Container */
.container { max-width: 960px; margin: 0 auto; padding: 28px 20px; }

/* Pages SPA */
.page { display: none; }
.page.active { display: block; }

/* Cards */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  transition: 0.12s;
}
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 12px; margin: 16px 0;
}
.card-feature {
  text-align: center; padding: 28px 16px; cursor: pointer;
}
.card-feature:hover { border-color: var(--blue); }
.card-feature .icon { font-size: 28px; margin-bottom: 10px; }
.card-feature h3 { font-size: 15px; margin-bottom: 4px; }
.card-feature p { font-size: 12px; color: var(--text-muted); }

/* Buttons */
.btn {
  display: inline-flex; align-items: center; gap: 5px;
  padding: 8px 20px; border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 13px; font-weight: 600;
  background: var(--bg-card); color: var(--text-primary);
  cursor: pointer; transition: 0.12s;
}
.btn:hover { border-color: var(--blue); background: var(--bg-hover); }
.btn-primary { background: var(--blue); color: #000; border-color: var(--blue); }
.btn-primary:hover { opacity: 0.85; }
.btn-danger { border-color: var(--red); color: var(--red); }
.btn-danger:hover { background: var(--red); color: #fff; }
.btn-sm { padding: 5px 12px; font-size: 12px; }
.btn:disabled { opacity: 0.4; cursor: not-allowed; }

/* Hero */
.hero { text-align: center; padding: 36px 16px 24px; }
.hero h1 { font-size: 36px; font-weight: 800; margin-bottom: 6px; }
.hero h1 span { color: var(--blue); }
.hero .tagline { font-size: 18px; font-weight: 700; margin-bottom: 8px; }
.hero .desc { font-size: 14px; color: var(--text-secondary); max-width: 520px; margin: 0 auto 20px; line-height: 1.7; }

.badges { display: flex; gap: 6px; justify-content: center; flex-wrap: wrap; margin-bottom: 24px; }
.badge {
  padding: 3px 12px; border-radius: 14px;
  font-size: 11px; font-weight: 500;
  background: rgba(79,195,247,0.08); color: var(--blue);
  border: 1px solid rgba(79,195,247,0.15);
}

/* Stats */
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(120px,1fr)); gap: 10px; margin: 16px 0; }
.stat-card { text-align: center; padding: 16px; }
.stat-card .num { font-size: 24px; font-weight: 800; }
.stat-card .lbl { font-size: 11px; color: var(--text-muted); margin-top: 2px; }

/* Exam */
.exam-header {
  display: flex; justify-content: space-between; align-items: center;
  margin-bottom: 16px; padding-bottom: 12px;
  border-bottom: 1px solid var(--border); flex-wrap: wrap; gap: 8px;
}
.exam-progress { display: flex; align-items: center; gap: 10px; font-size: 13px; color: var(--text-muted); }
.progress-bar { flex: 1; height: 5px; background: var(--bg-hover); border-radius: 3px; overflow: hidden; min-width: 100px; }
.progress-fill { height: 100%; background: var(--blue); transition: width 0.3s; border-radius: 3px; }
.timer { font-family: 'SF Mono', monospace; font-size: 20px; font-weight: 700; min-width: 80px; text-align: right; }
.timer-warning { color: var(--orange); }
.timer-critical { color: var(--red); animation: blink 0.8s infinite; }
@keyframes blink { 50% { opacity: 0.3; } }

.q-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 28px 24px; margin-bottom: 12px;
}
.q-meta { display: flex; gap: 8px; align-items: center; margin-bottom: 16px; font-size: 13px; }
.domain-badge { padding: 3px 10px; border-radius: 8px; font-size: 12px; font-weight: 600; }
.diff-badge { padding: 3px 10px; border-radius: 8px; font-size: 12px; font-weight: 600; }

.dn-nf { background: #1b5e20; color: #a5d6a7; }
.dn-na { background: #0d47a1; color: #90caf9; }
.dn-ic { background: #b71c1c; color: #ef9a9a; }
.dn-is { background: #4a148c; color: #ce93d8; }
.dn-sf { background: #e65100; color: #ffcc80; }
.dn-ap { background: #004d40; color: #80cbc4; }

.di-easy { background: #1b5e20; color: #a5d6a7; }
.di-medium { background: #e65100; color: #ffcc80; }
.di-hard { background: #b71c1c; color: #ef9a9a; }

.q-text { font-size: 17px; line-height: 1.8; margin-bottom: 20px; }

.option {
  display: block; padding: 14px 18px; margin-bottom: 8px;
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  cursor: pointer; transition: 0.12s; font-size: 16px; line-height: 1.5;
}
.option:hover { border-color: var(--blue); background: var(--bg-hover); }
.option.sel { border-color: var(--blue); background: rgba(79,195,247,0.08); }
.option.correct { border-color: var(--green); background: rgba(102,187,106,0.08); }
.option.wrong { border-color: var(--red); background: rgba(239,83,80,0.08); }
.option.missed { border-color: var(--orange); background: rgba(255,167,38,0.08); border-style: dashed; }

.qa { display: flex; gap: 6px; justify-content: space-between; margin-top: 16px; flex-wrap: wrap; }
.qa-l, .qa-r { display: flex; gap: 6px; flex-wrap: wrap; }

/* Answer Sheet */
.sheet { display: grid; grid-template-columns: repeat(auto-fill, minmax(32px,1fr)); gap: 4px; margin: 12px 0; }
.si {
  width: 32px; height: 32px; display: flex; align-items: center; justify-content: center;
  border: 1px solid var(--border); border-radius: 4px;
  font-size: 11px; font-weight: 600; cursor: pointer; transition: 0.12s;
}
.si:hover { border-color: var(--blue); }
.si.cur { border-color: var(--blue); background: rgba(79,195,247,0.1); }
.si.done { background: var(--blue); color: #000; }
.si.marked { border-color: var(--orange); }
.si.correct { background: var(--green); color: #000; }
.si.wrong { background: var(--red); color: #fff; }

/* Result */
.result { text-align: center; padding: 32px 16px; }
.result .big { font-size: 64px; font-weight: 800; }
.result .label { font-size: 16px; color: var(--text-secondary); margin-top: 4px; }
.result .sub { font-size: 13px; color: var(--text-muted); margin-top: 6px; }

.ds-grid { display: grid; grid-template-columns: repeat(auto-fit,minmax(120px,1fr)); gap: 10px; margin: 20px 0; }
.ds-card { padding: 14px; border-radius: var(--radius-sm); text-align: center; }
.ds-card .pct { font-size: 24px; font-weight: 800; }
.ds-card .name { font-size: 11px; margin-top: 4px; opacity: 0.85; }
.ds-card .cnt { font-size: 10px; opacity: 0.7; }

/* Wrong answers */
.wi { border-left: 3px solid var(--red); }
.wi.mastered { border-left-color: var(--green); }
.wi.almost { border-left-color: var(--orange); }
.wa-display { margin: 8px 0; padding: 8px 12px; border-radius: var(--radius-sm); font-size: 13px; }
.wa-user { background: rgba(239,83,80,0.08); color: var(--red); }
.wa-correct { background: rgba(102,187,106,0.08); color: var(--green); }

/* Filter */
.fbar { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 12px; align-items: center; }
.fbar select, .fbar input {
  padding: 5px 10px; background: var(--bg-input);
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  color: var(--text-primary); font-size: 13px;
}
.fbar select:focus, .fbar input:focus { outline: none; border-color: var(--blue); }

/* Settings */
.ss { margin-bottom: 24px; }
.ss h2 { font-size: 15px; margin-bottom: 12px; padding-bottom: 6px; border-bottom: 1px solid var(--border); }
.sr { display: flex; justify-content: space-between; align-items: center; padding: 10px 0; border-bottom: 1px solid var(--border); gap: 8px; }
.sr:last-child { border-bottom: none; }
.sr .lbl { font-size: 14px; }
.sr .desc { font-size: 12px; color: var(--text-muted); }

/* Empty state */
.empty { text-align: center; padding: 48px 16px; color: var(--text-muted); }
.empty .icon { font-size: 40px; margin-bottom: 12px; }
.empty p { margin-bottom: 16px; }

/* Modal */
.overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.55); display: none; align-items: center; justify-content: center; z-index: 200; }
.overlay.open { display: flex; }
.modal { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px; max-width: 400px; width: 90%; }
.modal h3 { margin-bottom: 10px; }
.modal p { font-size: 14px; color: var(--text-secondary); margin-bottom: 16px; }
.modal-actions { display: flex; gap: 6px; justify-content: flex-end; }

/* Toast */
.toast {
  position: fixed; bottom: 20px; left: 50%; transform: translateX(-50%);
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: 6px; padding: 8px 16px; font-size: 13px;
  z-index: 300; display: none; box-shadow: 0 4px 20px rgba(0,0,0,0.4);
}

/* Planner */
.wc { margin-bottom: 14px; }
.wh { display: flex; justify-content: space-between; margin-bottom: 10px; }
.wh h3 { font-size: 15px; }
.wh .h { font-size: 12px; color: var(--text-muted); }
.ti { display: flex; align-items: center; gap: 8px; padding: 6px 0; font-size: 13px; border-bottom: 1px solid var(--border); }
.ti:last-child { border-bottom: none; }
.ti .day { font-size: 11px; color: var(--text-muted); min-width: 40px; }
.ti .tp { font-size: 10px; padding: 1px 6px; border-radius: 6px; font-weight: 600; }
.ti .tp-read { background: rgba(79,195,247,0.1); color: var(--blue); }
.ti .tp-practice { background: rgba(102,187,106,0.1); color: var(--green); }
.ti .tp-lab { background: rgba(255,167,38,0.1); color: var(--orange); }

/* Theme toggle */
.theme-tog { display: flex; border: 1px solid var(--border); border-radius: var(--radius-sm); overflow: hidden; }
.theme-opt { padding: 5px 12px; font-size: 12px; cursor: pointer; border: none; background: transparent; color: var(--text-secondary); }
.theme-opt.active { background: var(--blue); color: #000; font-weight: 600; }

/* ============================================================
   Vendor-specific theming (Cisco blue / Huawei red)
   ============================================================ */

/* Vendor sections */
.vendor-cisco { --vendor-color: var(--blue); }
.vendor-huawei { --vendor-color: var(--huawei-red); }

.vendor-heading {
  font-size: 15px;
  margin: 16px 0 10px;
  padding-left: 10px;
  border-left: 3px solid var(--vendor-color);
  color: var(--vendor-color);
}

.vendor-label {
  font-size: 13px;
  font-weight: 700;
  margin-bottom: 6px;
  color: var(--vendor-color);
}

/* Vendor buttons — inherit accent from parent .vendor-xxx class */
.btn-vendor {
  background: var(--vendor-color);
  color: #fff;
  border-color: var(--vendor-color);
}
.btn-vendor:hover { opacity: 0.85; }

/* Vendor filter tabs */
.vendor-filter {
  display: flex;
  gap: 6px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.vf-btn {
  padding: 5px 16px;
  border-radius: 14px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text-secondary);
  transition: 0.12s;
}
.vf-btn:hover { border-color: var(--text-muted); color: var(--text-primary); }
.vf-btn.active { color: #000; border-color: var(--blue); background: var(--blue); }
.vf-btn[data-vf="huawei"].active { color: #fff; border-color: var(--huawei-red); background: var(--huawei-red); }

/* Vendor badge on exam cards */
.vendor-badge {
  display: inline-block;
  font-size: 10px;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: 8px;
  margin-left: 6px;
}
.vendor-badge.v-cisco { background: rgba(79,195,247,0.12); color: var(--blue); }
.vendor-badge.v-huawei { background: rgba(229,57,53,0.12); color: var(--huawei-red); }

/* Home vendor stats */
.vendor-stats {
  display: flex;
  gap: 10px;
  justify-content: center;
  margin-top: 8px;
  flex-wrap: wrap;
}
.vendor-stat {
  font-size: 12px;
  padding: 3px 12px;
  border-radius: 14px;
  font-weight: 600;
}
.vendor-stat.v-cisco { background: rgba(79,195,247,0.08); color: var(--blue); border: 1px solid rgba(79,195,247,0.15); }
.vendor-stat.v-huawei { background: rgba(229,57,53,0.08); color: var(--huawei-red); border: 1px solid rgba(229,57,53,0.15); }

/* ============================================================
   Multi-type questions (drag, fill, multiple)
   ============================================================ */
.drag-list { display:flex; flex-direction:column; gap:6px; margin-top:8px; }
.drag-item { display:flex; align-items:center; gap:10px; padding:10px 14px; background:var(--bg-input); border:1px solid var(--border); border-radius:var(--radius-sm); }
.drag-pos { width:24px; height:24px; display:flex; align-items:center; justify-content:center; background:var(--bg-hover); border-radius:12px; font-size:12px; font-weight:700; flex-shrink:0; }
.drag-text { flex:1; font-size:14px; }
.drag-arrows { display:flex; gap:4px; }
.drag-arrows .btn { padding:2px 8px; font-size:11px; min-width:28px; }

.fill-input:focus { outline:none; border-color:var(--accent, var(--blue)) !important; }

/* Responsive */
@media (max-width: 768px) {
  .container { padding: 16px 12px; }
  .hero { padding: 32px 12px 20px; }
  .hero h1 { font-size: 24px; }
  .nav { padding: 0 10px; }
  .nav-link { padding: 5px 8px; font-size: 12px; }
  .card-grid { grid-template-columns: repeat(2,1fr); gap: 8px; }
  .ds-grid { grid-template-columns: repeat(3,1fr); gap: 6px; }
  .stats { grid-template-columns: repeat(2,1fr); }
  .q-card { padding: 16px; }
  .result .big { font-size: 44px; }
  .qa { flex-direction: column; }
  .qa-r { width: 100%; }
  .fbar { flex-direction: column; }
  .fbar select, .fbar input { width: 100%; }
  .sr { flex-direction: column; align-items: flex-start; }
}
@media (max-width: 480px) {
  .card-grid { grid-template-columns: 1fr; }
  .ds-grid { grid-template-columns: repeat(2,1fr); }
  .exam-header { flex-direction: column; align-items: flex-start; }
}