:root {
  --bg: #f8fafc;
  --panel: #ffffff;
  --panel-border: #e2e8f0;
  --text: #1e293b;
  --muted: #64748b;
  --accent: #0ea5e9;
  --accent-2: #0284c7;
  --accent-light: #e0f2fe;
  --success: #16a34a;
  --danger: #dc2626;
  --warning: #eab308;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.1);
  --radius: 12px;
}

* { box-sizing: border-box; }

html { font-size: 100%; }

body {
  margin: 0;
  font-family: Inter, system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent-2); }

/* ---- Navbar ---- */
.site-nav {
  background: var(--panel);
  border-bottom: 1px solid var(--panel-border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}
.site-nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 16px;
  display: flex;
  align-items: center;
  height: 56px;
  gap: 8px;
}
.site-nav-logo {
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--accent);
  text-decoration: none;
  margin-right: auto;
  letter-spacing: -0.02em;
}
.site-nav-logo:hover { color: var(--accent-2); }
.site-nav-links { display: flex; align-items: center; gap: 4px; }
.site-nav-links a {
  color: var(--muted);
  font-weight: 600;
  font-size: 0.9rem;
  padding: 6px 12px;
  border-radius: 8px;
  transition: background 0.15s, color 0.15s;
}
.site-nav-links a:hover { background: var(--accent-light); color: var(--accent-2); }
.site-nav-links a.active { color: var(--accent); background: var(--accent-light); }
.nav-account {
  position: relative;
  margin-left: 4px;
}
.nav-account-btn {
  background: var(--accent-light);
  border: 1px solid var(--panel-border);
  border-radius: 50%;
  width: 36px; height: 36px;
  display: flex; align-items: center; justify-content: center;
  cursor: pointer;
  color: var(--accent);
  transition: border-color 0.15s, background 0.15s;
}
.nav-account-btn:hover, .nav-account.open .nav-account-btn {
  border-color: var(--accent);
  background: var(--accent);
  color: #fff;
}
.nav-account-btn svg { width: 18px; height: 18px; fill: currentColor; }
.nav-account-dropdown {
  display: none;
  position: absolute;
  top: calc(100% + 6px);
  right: 0;
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  min-width: 170px;
  box-shadow: var(--shadow-lg);
  overflow: hidden;
}
.nav-account.open .nav-account-dropdown { display: block; }
.nav-account-dropdown .pts-label {
  padding: 10px 14px;
  font-size: 0.8rem;
  color: var(--accent);
  font-weight: 700;
  border-bottom: 1px solid var(--panel-border);
  background: var(--accent-light);
}
.nav-account-dropdown a {
  display: block;
  padding: 10px 14px;
  color: var(--text);
  font-weight: 600;
  font-size: 0.9rem;
}
.nav-account-dropdown a:hover { background: var(--bg); color: var(--accent); }
.nav-cta {
  background: var(--accent);
  color: #fff !important;
  padding: 8px 16px;
  border-radius: 999px;
  font-weight: 700;
  font-size: 0.9rem;
  margin-left: 4px;
  transition: background 0.15s;
}
.nav-cta:hover { background: var(--accent-2); color: #fff !important; }

/* Mobile hamburger */
.nav-hamburger {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 6px;
  color: var(--text);
}
.nav-hamburger svg { width: 24px; height: 24px; }

@media (max-width: 700px) {
  .site-nav-links { display: none; }
  .site-nav-links.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 56px; left: 0; right: 0;
    background: var(--panel);
    border-bottom: 1px solid var(--panel-border);
    box-shadow: var(--shadow-md);
    padding: 8px 16px 12px;
    gap: 2px;
  }
  .site-nav-links.open a { padding: 10px 12px; font-size: 1rem; }
  .nav-hamburger { display: block; }
  .nav-cta { display: none; }
  .site-nav-links.open .nav-cta { display: block; text-align: center; margin: 8px 0 0; }
}

/* ---- Layout ---- */
.app {
  max-width: 980px;
  width: 100%;
  margin: 0 auto;
  padding: 24px 16px 48px;
  overflow-x: hidden;
}
/* Lecture page: mobile-first with safe-area for notched devices */
.app.lecture-page {
  max-width: 100%;
  padding: 12px 12px 32px;
  padding-left: max(12px, env(safe-area-inset-left));
  padding-right: max(12px, env(safe-area-inset-right));
  padding-bottom: max(32px, env(safe-area-inset-bottom));
  box-sizing: border-box;
}
@media (min-width: 480px) {
  .app.lecture-page {
    padding-left: max(14px, env(safe-area-inset-left));
    padding-right: max(14px, env(safe-area-inset-right));
  }
}
@media (min-width: 640px) {
  .app.lecture-page {
    max-width: 980px;
    padding: 24px 16px 48px;
    padding-left: max(16px, env(safe-area-inset-left));
    padding-right: max(16px, env(safe-area-inset-right));
    padding-bottom: max(48px, env(safe-area-inset-bottom));
  }
}

.hero { margin-bottom: 8px; }
.hero h1 { margin: 0; font-size: 1.75rem; font-weight: 800; letter-spacing: -0.02em; }
.hero p { color: var(--muted); margin-top: 6px; font-size: 0.95rem; }

.panel {
  margin-top: 16px;
  border-radius: var(--radius);
  border: 1px solid var(--panel-border);
  background: var(--panel);
  padding: 20px;
  box-shadow: var(--shadow-sm);
  overflow-x: hidden;
}

.lecture-grid > div {
  min-width: 0;
}

/* ---- Buttons ---- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: 1px solid var(--panel-border);
  background: var(--panel);
  color: var(--text);
  padding: 10px 16px;
  border-radius: 10px;
  cursor: pointer;
  font-weight: 700;
  font-size: 0.95rem;
  transition: background 0.15s, border-color 0.15s;
}
.btn:hover { background: var(--bg); border-color: var(--muted); }
.btn.primary {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.btn.primary:hover { background: var(--accent-2); border-color: var(--accent-2); }
.btn.outline {
  background: transparent;
  border: 1px solid var(--panel-border);
}
.btn.outline:hover { background: var(--bg); }

/* ---- Forms ---- */
label {
  display: block;
  margin: 12px 0 6px;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text);
}
input, textarea, select {
  width: 100%;
  border: 1px solid var(--panel-border);
  border-radius: 10px;
  background: var(--panel);
  color: var(--text);
  padding: 10px 12px;
  font-size: 0.95rem;
  transition: border-color 0.15s, box-shadow 0.15s;
}
input:focus, textarea:focus, select:focus {
  border-color: var(--accent);
  outline: none;
  box-shadow: 0 0 0 3px var(--accent-light);
}

/* ---- Grid ---- */
.grid-2 { display: grid; gap: 12px; grid-template-columns: repeat(2, minmax(0, 1fr)); }

.actions { margin-top: 14px; display: flex; gap: 8px; flex-wrap: wrap; }

/* ---- Tabs ---- */
.tabs { display: flex; gap: 6px; flex-wrap: wrap; }
.tab {
  border: 1px solid var(--panel-border);
  background: var(--panel);
  color: var(--muted);
  border-radius: 999px;
  padding: 8px 16px;
  cursor: pointer;
  font-weight: 700;
  font-size: 0.9rem;
  transition: background 0.15s, color 0.15s;
}
.tab:hover { color: var(--text); background: var(--bg); }
.tab.is-active { background: var(--accent); color: #fff; border-color: var(--accent); }
.tab-content { display: none; }
.tab-content.is-active { display: block; }

/* ---- Quiz option buttons ---- */
.option-btn {
  display: block;
  width: 100%;
  text-align: left;
  border: 2px solid var(--panel-border);
  border-radius: 10px;
  background: var(--panel);
  color: var(--text);
  padding: 14px 16px;
  cursor: pointer;
  font-weight: 600;
  font-size: 1rem;
  min-height: 52px;
  transition: border-color 0.15s, background 0.15s;
}
.option-btn:hover:not(:disabled) {
  border-color: var(--accent);
  background: var(--accent-light);
}
.option-btn:disabled { cursor: default; opacity: 0.7; }
.option-btn.correct { border-color: var(--success); background: #dcfce7; }
.option-btn.wrong, .option-btn.incorrect { border-color: var(--danger); background: #fef2f2; opacity: 0.7; }

/* Contest colored option buttons */
.option-btn.opt-0 { border-color: #ef4444; background: #fef2f2; }
.option-btn.opt-1 { border-color: #3b82f6; background: #eff6ff; }
.option-btn.opt-2 { border-color: #eab308; background: #fefce8; }
.option-btn.opt-3 { border-color: #22c55e; background: #f0fdf4; }
.option-btn.opt-0:hover:not(:disabled) { background: #fee2e2; }
.option-btn.opt-1:hover:not(:disabled) { background: #dbeafe; }
.option-btn.opt-2:hover:not(:disabled) { background: #fef9c3; }
.option-btn.opt-3:hover:not(:disabled) { background: #dcfce7; }

/* ---- Question timer ---- */
.question-timer { font-size: 2rem; font-weight: 800; color: var(--accent); margin-bottom: 8px; }

/* ---- Question card ---- */
.question-card {
  margin-top: 12px;
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  background: var(--panel);
  padding: 16px;
  box-shadow: var(--shadow-sm);
}

/* ---- Results overlay / modal ---- */
.results-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  z-index: 200;
  justify-content: center;
  align-items: center;
  padding: 1rem;
  backdrop-filter: blur(4px);
}
.results-overlay.active { display: flex; }
.results-modal {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 16px;
  padding: 2rem;
  max-width: 480px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  box-shadow: var(--shadow-lg);
  animation: popIn 0.25s ease;
}
@keyframes popIn { from { transform: scale(0.9); opacity: 0; } to { transform: scale(1); opacity: 1; } }
.results-modal h2 { margin: 0 0 0.5rem; font-size: 1.3rem; }
.results-correct { color: var(--success); font-size: 1.05rem; font-weight: 700; margin-bottom: 0.25rem; }
.results-who { color: var(--muted); font-size: 0.9rem; margin-bottom: 1rem; }
.results-divider { border: none; border-top: 1px solid var(--panel-border); margin: 1rem 0; }
.results-rank { display: flex; align-items: center; gap: 0.75rem; padding: 0.6rem 0; border-bottom: 1px solid var(--panel-border); }
.results-rank:last-child { border-bottom: none; }
.results-rank .rank-pos {
  width: 28px; height: 28px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-weight: 700; font-size: 0.85rem; flex-shrink: 0;
}
.rank-1 { background: #fef9c3; color: #854d0e; }
.rank-2 { background: #f1f5f9; color: #475569; }
.rank-3 { background: #fef3c7; color: #92400e; }
.rank-default { background: var(--bg); color: var(--muted); }
.results-rank .rank-name { flex: 1; font-weight: 600; }
.results-rank .rank-score { color: var(--accent); font-weight: 700; }
.results-waiting { text-align: center; color: var(--muted); font-size: 0.9rem; margin-top: 1rem; }

/* ---- Misc ---- */
.output {
  margin-top: 12px;
  background: var(--bg);
  border: 1px solid var(--panel-border);
  color: var(--text);
  border-radius: 10px;
  padding: 12px;
  min-height: 80px;
  white-space: pre-wrap;
}
.hint { margin: 0; color: var(--muted); font-size: 0.9rem; }
.hidden { display: none; }

.correct-answer-display {
  margin-top: 12px;
  padding: 12px;
  background: var(--accent-light);
  border-radius: 10px;
  color: var(--accent-2);
  font-weight: 600;
}

/* ---- Podium ---- */
.podium { display: flex; align-items: flex-end; justify-content: center; gap: 1rem; margin: 2rem 0; }
.podium .place { text-align: center; padding: 1rem; }
.podium .place-1 { order: 2; }
.podium .place-2 { order: 1; }
.podium .place-3 { order: 3; }
.podium .height {
  background: linear-gradient(180deg, var(--accent-light) 0%, var(--panel) 100%);
  border-radius: 8px 8px 0 0;
  margin-bottom: 0.5rem;
  border: 1px solid var(--panel-border);
}
.podium .place-1 .height { height: 120px; }
.podium .place-2 .height { height: 90px; }
.podium .place-3 .height { height: 60px; }

/* ---- Loading spinner ---- */
@keyframes spin { to { transform: rotate(360deg); } }
.match-spinner {
  display: inline-block;
  width: 20px; height: 20px;
  border: 2px solid var(--panel-border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  vertical-align: middle;
}

/* ---- Responsive ---- */
@media (max-width: 760px) {
  .grid-2 { grid-template-columns: 1fr; }
  .app { padding: 16px 12px 32px; }
  .hero h1 { font-size: 1.35rem; }
  .panel { padding: 14px; }
  .option-btn { padding: 12px 14px; font-size: 0.95rem; }
  .btn { padding: 10px 12px; font-size: 0.95rem; }
  .question-timer { font-size: 1.5rem; }
  input, textarea, select { font-size: 16px; }
  .podium { gap: 0.5rem; }
  .podium .place { padding: 0.5rem; }
  .podium .place-1 .height { height: 80px; }
  .podium .place-2 .height { height: 60px; }
  .podium .place-3 .height { height: 40px; }
  .results-modal { padding: 1.25rem; margin: 0.5rem; }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 1.15rem; }
  .tabs { overflow-x: auto; -webkit-overflow-scrolling: touch; flex-wrap: nowrap; }
  .tab { white-space: nowrap; padding: 8px 12px; font-size: 0.85rem; }
}