/* =====================================================
   AI ADAPTIVE EXAM SYSTEM — Main Stylesheet
   "Liquid Glass" theme — Dark / Light via data-theme
===================================================== */

/* Google Font */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap');

/* ── Theme variables ── */
:root {
  --bg:        #07070a;
  --bg2:       #0d0d12;
  --bg3:       rgba(255,255,255,0.055);
  --card:      rgba(255,255,255,0.055);
  --card-strong: rgba(255,255,255,0.09);
  --border:    rgba(255,255,255,0.12);
  --border2:   rgba(255,255,255,0.22);
  --text:      #f3f3f8;
  --text2:     #b3b3c4;
  --text3:     #78788c;
  --accent:    #38bdf8;
  --accent-h:  #0ea5e9;
  --accent2:   #8b5cf6;
  --blue-glow: rgba(56,189,248,0.20);
  --green:     #22c55e;
  --green-bg:  rgba(34,197,94,0.16);
  --red:       #ef4444;
  --red-bg:    rgba(239,68,68,0.16);
  --yellow:    #eab308;
  --yellow-bg: rgba(234,179,8,0.16);
  --white:     #ffffff;
  --radius:    22px;
  --radius-sm: 14px;
  --shadow:    0 10px 34px rgba(0,0,0,0.45), inset 0 1px 0 rgba(255,255,255,0.07);
  --glass-blur: blur(22px) saturate(180%);
  --glass-blur-strong: blur(30px) saturate(200%);
  --font:      'Inter', system-ui, sans-serif;
  --mono:      'JetBrains Mono', monospace;
  --transition: 0.22s cubic-bezier(.4,0,.2,1);

  /* background glow colors (dark) */
  --glow1: rgba(34,197,94,0.30);
  --glow2: rgba(249,115,22,0.24);
  --glow3: rgba(139,92,246,0.28);
  --glow4: rgba(56,189,248,0.22);
  --glow-blend: screen;
  --glow-opacity: 1;
  /* Subtle top-left specular highlight — the "light catching glass" look.
     Light theme overrides this with a much brighter version below. */
  --glass-sheen: linear-gradient(155deg, rgba(255,255,255,0.14), rgba(255,255,255,0) 45%);
}

[data-theme="light"] {
  --bg:        #eef1f7;
  --bg2:       #f6f7fb;
  --bg3:       rgba(255,255,255,0.55);
  --card:      rgba(255,255,255,0.55);
  --card-strong: rgba(255,255,255,0.75);
  --border:    rgba(255,255,255,0.75);
  --border2:   rgba(110,120,150,0.28);
  --text:      #12131c;
  --text2:     #4a4f66;
  --text3:     #8489a0;
  --blue-glow: rgba(14,165,233,0.14);
  --green-bg:  rgba(34,197,94,0.16);
  --red-bg:    rgba(239,68,68,0.13);
  --yellow-bg: rgba(234,179,8,0.16);
  --shadow:    0 10px 30px rgba(31,38,135,0.14), inset 0 1px 0 rgba(255,255,255,0.85);
  /* A brighter, more directional gloss than dark theme's — this is the
     specular "light catching the glass" highlight that makes a panel read
     as glass instead of a flat tinted rectangle. */
  --glass-sheen: linear-gradient(155deg, rgba(255,255,255,0.75), rgba(255,255,255,0.05) 40%, rgba(255,255,255,0) 60%);

  /* Liquid Glass on light backgrounds relies on vivid color bleeding
     through the frosted panels — 0.55 read as washed-out/flat, so this is
     pushed up to actually show colored light through the glass. */
  --glow1: rgba(74,222,128,0.55);
  --glow2: rgba(251,146,60,0.45);
  --glow3: rgba(167,139,250,0.5);
  --glow4: rgba(56,189,248,0.48);
  --glow-blend: normal;
  --glow-opacity: 0.85;
}

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

html { scroll-behavior: smooth; background: var(--bg); }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  font-size: 14px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  transition: background var(--transition), color var(--transition);
  position: relative;
  overflow-x: hidden;
}

/* ── Liquid glass ambient background ── */
body::before {
  content: '';
  position: fixed;
  inset: -15%;
  z-index: -2;
  pointer-events: none;
  background:
    radial-gradient(circle at 14% 18%, var(--glow1), transparent 42%),
    radial-gradient(circle at 86% 12%, var(--glow2), transparent 44%),
    radial-gradient(circle at 46% 82%, var(--glow3), transparent 46%),
    radial-gradient(circle at 90% 78%, var(--glow4), transparent 42%);
  filter: blur(95px);
  opacity: var(--glow-opacity);
  mix-blend-mode: var(--glow-blend);
  animation: drift 26s ease-in-out infinite alternate;
  transition: opacity var(--transition);
}
body::after {
  content: '';
  position: fixed;
  inset: 0;
  z-index: -3;
  background: var(--bg);
}
@keyframes drift {
  0%   { transform: translate(0,0) scale(1); }
  50%  { transform: translate(-2%, 2%) scale(1.05); }
  100% { transform: translate(2%, -2%) scale(1.08); }
}
@media (prefers-reduced-motion: reduce) {
  body::before { animation: none; }
}

a { color: var(--accent); text-decoration: none; }
a:hover { opacity: 0.8; }

::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border2); border-radius: 3px; }

/* ── Layout helpers ── */
.page-center {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px 16px;
}

.hidden { display: none !important; }

/* ── Cards (glass panels) ── */
.card {
  background: var(--glass-sheen), var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
}

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  padding: 10px 20px;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  font-family: var(--font);
  transition: all var(--transition);
  white-space: nowrap;
  letter-spacing: 0.2px;
  text-decoration: none;
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
}
.btn:disabled { opacity: 0.45; cursor: not-allowed; transform: none !important; }
.btn:not(:disabled):hover { transform: translateY(-1px); }

.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  border-color: rgba(255,255,255,0.25);
  box-shadow: 0 6px 20px var(--blue-glow), inset 0 1px 0 rgba(255,255,255,0.35);
}
.btn-primary:not(:disabled):hover { filter: brightness(1.08); box-shadow: 0 8px 26px var(--blue-glow), inset 0 1px 0 rgba(255,255,255,0.4); }
.btn-secondary {
  background: linear-gradient(135deg, var(--accent2), #6d28d9);
  color: #fff;
  border-color: rgba(255,255,255,0.25);
  box-shadow: 0 6px 20px rgba(139,92,246,0.25), inset 0 1px 0 rgba(255,255,255,0.3);
}
.btn-ghost {
  background: var(--card);
  color: var(--text);
  border-color: var(--border);
}
.btn-ghost:not(:disabled):hover { background: var(--card-strong); border-color: var(--border2); }
.btn-danger  { background: linear-gradient(135deg, var(--red), #b91c1c); color: #fff; border-color: rgba(255,255,255,0.2); box-shadow: 0 6px 18px rgba(239,68,68,0.25); }
.btn-success { background: linear-gradient(135deg, var(--green), #15803d); color: #fff; border-color: rgba(255,255,255,0.2); box-shadow: 0 6px 18px rgba(34,197,94,0.25); }
.btn-full { width: 100%; }
.btn-sm   { padding: 7px 14px; font-size: 12px; }

/* ── Inputs ── */
.field { margin-bottom: 16px; }
.field label {
  display: block;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: var(--text2);
  margin-bottom: 6px;
}
.field input,
.field select,
.field textarea {
  width: 100%;
  padding: 10px 13px;
  background: var(--bg3);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  font-size: 14px;
  font-family: var(--font);
  outline: none;
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  transition: border-color var(--transition), box-shadow var(--transition), background var(--transition);
}
.field input:focus,
.field select:focus,
.field textarea:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--blue-glow);
  background: var(--card-strong);
}
.field .err { font-size: 11px; color: var(--red); margin-top: 4px; min-height: 15px; }
.field select option { background: var(--bg2); color: var(--text); }

/* ── Google button ── */
.google-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  width: 100%;
  padding: 10px 16px;
  background: rgba(255,255,255,0.92);
  border: 1.5px solid rgba(255,255,255,0.5);
  border-radius: var(--radius-sm);
  color: #333;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  font-family: var(--font);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  transition: box-shadow var(--transition), transform var(--transition);
  text-decoration: none;
}
.google-btn:hover { box-shadow: 0 6px 22px rgba(0,0,0,0.25); transform: translateY(-1px); }
.google-btn img { width: 18px; height: 18px; }

/* ── Divider ── */
.divider {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 16px 0;
  color: var(--text3);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 1px;
}
.divider::before, .divider::after { content: ''; flex: 1; height: 1px; background: var(--border); }

/* ── Badges ── */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.3px;
  border: 1px solid transparent;
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
}
.badge-blue   { background: rgba(56,189,248,0.16); color: #7dd3fc; border-color: rgba(56,189,248,0.3); }
.badge-green  { background: var(--green-bg); color: #4ade80; border-color: rgba(34,197,94,0.3); }
.badge-yellow { background: var(--yellow-bg); color: #fbbf24; border-color: rgba(234,179,8,0.3); }
.badge-red    { background: var(--red-bg); color: #f87171; border-color: rgba(239,68,68,0.3); }
.badge-purple { background: rgba(139,92,246,0.16); color: #c4b5fd; border-color: rgba(139,92,246,0.3); }

[data-theme="light"] .badge-blue   { background: rgba(14,165,233,0.14); color: #0369a1; border-color: rgba(14,165,233,0.3); }
[data-theme="light"] .badge-green  { background: rgba(34,197,94,0.16); color: #15803d; border-color: rgba(34,197,94,0.3); }
[data-theme="light"] .badge-yellow { background: rgba(234,179,8,0.18); color: #a16207; border-color: rgba(234,179,8,0.3); }
[data-theme="light"] .badge-red    { background: rgba(239,68,68,0.14); color: #b91c1c; border-color: rgba(239,68,68,0.3); }
[data-theme="light"] .badge-purple { background: rgba(139,92,246,0.14); color: #6d28d9; border-color: rgba(139,92,246,0.3); }

/* ── Toast ── */
.toast {
  position: fixed;
  top: 16px;
  right: 16px;
  padding: 12px 18px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  font-weight: 600;
  z-index: 99999;
  opacity: 0;
  pointer-events: none;
  transform: translateY(-6px);
  transition: opacity 0.25s, transform 0.25s;
  max-width: 320px;
  box-shadow: var(--shadow);
  border: 1px solid transparent;
  backdrop-filter: var(--glass-blur-strong);
  -webkit-backdrop-filter: var(--glass-blur-strong);
}
.toast.show   { opacity: 1; transform: translateY(0); }
.toast.success { background: rgba(34,197,94,0.22);  color: #4ade80; border-color: rgba(34,197,94,0.35); }
.toast.error   { background: rgba(239,68,68,0.22);  color: #f87171; border-color: rgba(239,68,68,0.35); }
.toast.info    { background: rgba(56,189,248,0.22); color: #7dd3fc; border-color: rgba(56,189,248,0.35); }
.toast.warn    { background: rgba(234,179,8,0.22);  color: #fbbf24; border-color: rgba(234,179,8,0.35); }

[data-theme="light"] .toast.success { background: rgba(34,197,94,0.85);  color: #fff; border-color: rgba(34,197,94,0.4); }
[data-theme="light"] .toast.error   { background: rgba(239,68,68,0.85);  color: #fff; border-color: rgba(239,68,68,0.4); }
[data-theme="light"] .toast.info    { background: rgba(14,165,233,0.85); color: #fff; border-color: rgba(14,165,233,0.4); }

/* ── Spinner ── */
.spinner {
  width: 32px; height: 32px;
  border: 3px solid var(--border2);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.65s linear infinite;
  flex-shrink: 0;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── Progress bar ── */
.prog-wrap { background: var(--border); border-radius: 10px; height: 6px; overflow: hidden; backdrop-filter: var(--glass-blur); -webkit-backdrop-filter: var(--glass-blur); }
.prog-fill { height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent2)); border-radius: 10px; transition: width 0.4s ease; }

/* ── Theme toggle ── */
.theme-toggle {
  width: 38px; height: 38px;
  border: 1px solid var(--border);
  border-radius: 50%;
  background: var(--card);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  box-shadow: var(--shadow);
  transition: all var(--transition);
  flex-shrink: 0;
}
.theme-toggle:hover { border-color: var(--accent); transform: translateY(-1px); }

/* Mobile-only floating theme toggle (see home.html) — hidden on desktop
   where the sidebar's own theme-toggle button is visible instead. */
.mobile-theme-toggle { display: none; }

/* ── Rank colors ── */
.rank-S { color: #fbbf24; }
.rank-A { color: #a78bfa; }
.rank-B { color: #60a5fa; }
.rank-C { color: #34d399; }
.rank-D { color: #fb923c; }
.rank-F { color: #9ca3af; }

/* ── Step bar ── */
.step-bar { display: flex; align-items: center; margin-bottom: 32px; }
.step-item { display: flex; align-items: center; gap: 8px; }
.step-circle {
  width: 30px; height: 30px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-size: 12px; font-weight: 700; flex-shrink: 0;
  border: 2px solid var(--border2);
  color: var(--text3);
  background: var(--card);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  transition: all var(--transition);
}
.step-item.done   .step-circle { background: linear-gradient(135deg, var(--green), #15803d); border-color: transparent; color: #fff; }
.step-item.active .step-circle { background: linear-gradient(135deg, var(--accent), var(--accent2)); border-color: transparent; color: #fff; }
.step-label { font-size: 12px; font-weight: 600; color: var(--text3); }
.step-item.active .step-label { color: var(--text); }
.step-line { flex: 1; height: 1px; background: var(--border); margin: 0 6px; }
.step-line.done { background: var(--green); }

/* ── Table ── */
.tbl { width: 100%; border-collapse: collapse; }
.tbl th { font-size: 10px; font-weight: 700; letter-spacing: 1.2px; text-transform: uppercase; color: var(--text3); padding: 10px 14px; text-align: left; border-bottom: 1px solid var(--border); }
.tbl td { padding: 11px 14px; font-size: 13px; border-bottom: 1px solid var(--border); }
.tbl tr:last-child td { border-bottom: none; }
.tbl tr:hover td { background: var(--bg3); }

/* ── Pill select ── */
.pill-row { display: flex; gap: 8px; flex-wrap: wrap; }
.pill {
  padding: 8px 16px; border-radius: 999px;
  border: 1.5px solid var(--border2);
  background: var(--card);
  color: var(--text2);
  cursor: pointer; font-size: 13px; font-weight: 600;
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  transition: all var(--transition);
  user-select: none;
}
.pill.active { border-color: var(--accent); background: var(--blue-glow); color: var(--accent); box-shadow: 0 4px 14px var(--blue-glow); }
.pill:hover:not(.active) { border-color: var(--border2); color: var(--text); background: var(--card-strong); }

/* ── Dropdown ── */
.dropdown-wrap { position: relative; }
.dropdown-list {
  position: absolute; top: calc(100% + 6px);
  left: 0; right: 0;
  background: var(--card-strong);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  max-height: 210px; overflow-y: auto;
  z-index: 200; display: none;
  box-shadow: var(--shadow);
  backdrop-filter: var(--glass-blur-strong);
  -webkit-backdrop-filter: var(--glass-blur-strong);
}
.dropdown-list.open { display: block; }
.dropdown-item { padding: 9px 13px; font-size: 13px; cursor: pointer; color: var(--text); transition: background var(--transition); }
.dropdown-item:hover { background: var(--bg3); }
.selected-tag { margin-top: 7px; padding: 6px 12px; background: var(--blue-glow); border: 1px solid var(--accent); border-radius: var(--radius-sm); font-size: 12px; color: var(--accent); font-weight: 600; display: none; }

/* ── Class grid ── */
.class-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin-top: 12px; }
.class-chip {
  padding: 9px 6px; border-radius: var(--radius-sm); text-align: center;
  border: 1.5px solid var(--border); background: var(--card);
  color: var(--text2); cursor: pointer; font-size: 13px; font-weight: 600;
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  transition: all var(--transition);
}
.class-chip.active { border-color: var(--accent2); background: rgba(139,92,246,0.18); color: #c4b5fd; box-shadow: 0 4px 14px rgba(139,92,246,0.2); }

/* ── Photo zone ── */
.photo-zone {
  border: 2px dashed var(--border2); border-radius: var(--radius);
  padding: 28px; text-align: center; cursor: pointer;
  position: relative; background: var(--bg3);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  transition: border-color var(--transition), background var(--transition);
}
.photo-zone:hover { border-color: var(--accent); background: var(--card-strong); }
.photo-zone input[type="file"] { position: absolute; inset: 0; opacity: 0; cursor: pointer; width: 100%; height: 100%; }
.photo-preview { width: 100px; height: 100px; border-radius: 50%; object-fit: cover; margin: 0 auto 10px; display: none; border: 3px solid var(--accent); }

/* ── Home sidebar layout ── */
.app-layout { display: grid; grid-template-columns: 240px 1fr; min-height: 100vh; gap: 16px; padding: 16px; }
.sidebar {
  background: var(--glass-sheen), var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  display: flex; flex-direction: column;
  padding: 16px;
  position: sticky; top: 16px; height: calc(100vh - 32px); overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  box-shadow: var(--shadow);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
}
.sidebar-logo { display: flex; align-items: center; gap: 10px; padding: 8px 10px; margin-bottom: 20px; }
.sidebar-logo-icon { font-size: 22px; }
.sidebar-logo-text { font-size: 14px; font-weight: 800; color: var(--text); }
.sidebar-logo-text span { color: var(--accent); }
.nav-section-label { font-size: 10px; font-weight: 700; letter-spacing: 1.5px; text-transform: uppercase; color: var(--text3); padding: 12px 10px 4px; }
.nav-btn {
  display: flex; align-items: center; gap: 10px;
  padding: 9px 12px; border-radius: 999px;
  font-size: 13px; font-weight: 500; color: var(--text2);
  cursor: pointer; border: 1px solid transparent; background: transparent;
  font-family: var(--font); transition: all var(--transition);
  width: 100%; text-align: left;
}
.nav-btn:hover  { background: var(--bg3); color: var(--text); }
.nav-btn.active {
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  color: #fff;
  border-color: rgba(255,255,255,0.25);
  box-shadow: 0 6px 18px var(--blue-glow), inset 0 1px 0 rgba(255,255,255,0.3);
}
.nav-icon { font-size: 15px; width: 20px; text-align: center; flex-shrink: 0; }
.sidebar-bottom { margin-top: auto; padding-top: 12px; border-top: 1px solid var(--border); display: flex; flex-direction: column; gap: 6px; }
.user-chip { display: flex; align-items: center; gap: 10px; padding: 10px; border-radius: var(--radius-sm); background: var(--bg3); border: 1px solid var(--border); backdrop-filter: var(--glass-blur); -webkit-backdrop-filter: var(--glass-blur); }
.user-av { width: 32px; height: 32px; border-radius: 50%; background: linear-gradient(135deg, var(--accent), var(--accent2)); display: flex; align-items: center; justify-content: center; font-size: 13px; font-weight: 800; color: #fff; flex-shrink: 0; box-shadow: 0 2px 10px var(--blue-glow); }
.user-name { font-size: 12px; font-weight: 600; color: var(--text); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.user-email { font-size: 11px; color: var(--text3); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

.main-area { padding: 4px 4px 4px 0; overflow-y: auto; -webkit-overflow-scrolling: touch; background: transparent; }
.page-view { display: none; }
.page-view.active { display: block; }
.page-title { font-size: 1.4rem; font-weight: 800; color: var(--text); margin-bottom: 4px; }
.page-subtitle { font-size: 13px; color: var(--text2); margin-bottom: 24px; }

/* ── Stat cards ── */
.stat-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 12px; margin-bottom: 24px; }
.stat-card {
  padding: 18px; border-radius: var(--radius);
  background: var(--glass-sheen), var(--card); border: 1px solid var(--border);
  box-shadow: var(--shadow);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  transition: transform var(--transition), box-shadow var(--transition);
}
.stat-card:hover { transform: translateY(-2px); }
.stat-label { font-size: 10px; font-weight: 700; letter-spacing: 1.2px; text-transform: uppercase; color: var(--text3); margin-bottom: 6px; }
.stat-val   { font-size: 1.8rem; font-weight: 800; color: var(--text); line-height: 1; }
.stat-sub   { font-size: 11px; color: var(--text3); margin-top: 4px; }

/* ── Subject cards ── */
.subject-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 14px; }
.subject-card {
  padding: 20px; border-radius: var(--radius);
  background: var(--glass-sheen), var(--card); border: 1px solid var(--border);
  box-shadow: var(--shadow);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  cursor: pointer; transition: all var(--transition);
}
.subject-card:hover { border-color: var(--accent); transform: translateY(-3px); box-shadow: 0 12px 28px var(--blue-glow), inset 0 1px 0 rgba(255,255,255,0.1); }
.subj-icon { font-size: 28px; margin-bottom: 10px; }
.subj-name { font-size: 14px; font-weight: 700; color: var(--text); margin-bottom: 8px; }
.subj-meta { font-size: 11px; color: var(--text3); display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 10px; }
.diff-row { display: flex; gap: 5px; flex-wrap: wrap; }
.diff-chip {
  padding: 3px 10px; border-radius: 10px; font-size: 11px; font-weight: 600;
  cursor: pointer; border: 1px solid transparent;
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  transition: all var(--transition);
}
.diff-easy { background: var(--green-bg); color: #4ade80; border-color: rgba(34,197,94,0.3); }
.diff-mod  { background: var(--yellow-bg); color: #fbbf24; border-color: rgba(234,179,8,0.3); }
.diff-hard { background: var(--red-bg);   color: #f87171; border-color: rgba(239,68,68,0.3); }
.diff-chip:hover { filter: brightness(1.2); }

/* ── Responsive ── */

/* Tablets / small laptops */
@media (max-width: 1024px) {
  .app-layout { grid-template-columns: 200px 1fr; }
  .main-area { padding: 4px; }
  .subject-grid { grid-template-columns: repeat(auto-fill, minmax(170px, 1fr)); }
  .stat-grid { grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); }
}

/* Phones / narrow tablets */
@media (max-width: 768px) {
  /* backdrop-filter blur is expensive to recompute every frame, and this
     page uses it on nearly every card/button/chip — on Android especially,
     that was the actual cause of scroll lag (not padding/overflow settings).
     Fully disabling it made mobile lose the "liquid glass" look entirely
     (flat, opaque panels, no motion), which looks especially wrong in
     light theme. Instead, drop to a much cheaper blur radius here — small
     enough to stay smooth on scroll, but still visibly translucent/glassy. */
  :root {
    --glass-blur: blur(9px) saturate(150%);
    --glass-blur-strong: blur(13px) saturate(160%);
  }
  /* Same reasoning — keep the ambient glow moving (it's what makes the
     theme feel "liquid" instead of a static tinted background), just
     shrink the blur radius so it's cheaper to repaint each frame. */
  body::before {
    animation: drift 30s ease-in-out infinite alternate;
    filter: blur(55px);
  }

  /* ── Layout: content on top, fixed bottom nav bar ── */
  .app-layout {
    grid-template-columns: 1fr;
    grid-template-rows: 1fr auto;
    grid-template-areas: "main" "sidebar";
    height: 100vh;
    height: 100dvh;
    overflow: hidden;
    padding: 0;
    gap: 0;
  }
  .main-area {
    grid-area: main;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    overscroll-behavior-y: contain;
    /* bottom padding clears the fixed pill tab bar (64px tall, 12px from
       the bottom, plus shadow) with margin to spare */
    padding: 16px 14px 170px;
  }
  /* ── Bottom tab bar ── */
  .sidebar {
    grid-area: sidebar;
    position: fixed;
    bottom: 12px; left: 12px; right: 12px;
    top: auto;
    height: 64px;
    flex-direction: row;
    align-items: stretch;
    padding: 6px;
    border: 1px solid var(--border);
    border-radius: 999px;
    background: var(--card-strong);
    z-index: 500;
    overflow: visible;
    gap: 2px;
    box-shadow: 0 -6px 26px rgba(0,0,0,.35), var(--shadow);
    backdrop-filter: var(--glass-blur-strong);
    -webkit-backdrop-filter: var(--glass-blur-strong);
  }
  /* Hide things that don't belong in tab bar */
  .nav-section-label,
  .sidebar-logo,
  .sidebar-bottom { display: none; }

  /* Bring the theme toggle back as a floating button since sidebar-bottom
     (which normally holds it) is hidden in the bottom-tab-bar layout. */
  .mobile-theme-toggle {
    display: flex;
    position: fixed;
    top: 14px; right: 14px;
    z-index: 600; /* above the bottom tab bar (z-index 500) */
  }

  /* ── Each nav button: equal-width flex column ── */
  .nav-btn {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 3px;
    padding: 6px 2px;
    min-width: 0;
    width: auto;
    height: 100%;
    border-radius: 999px;
    font-size: 9.5px;
    font-weight: 600;
    color: var(--text3);
    letter-spacing: 0.2px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }
  .nav-btn .nav-icon {
    font-size: 18px;
    width: auto;
    display: block;
    line-height: 1;
  }
  .nav-btn:hover {
    background: var(--bg3);
    color: var(--text2);
  }
  .nav-btn.active {
    color: #fff;
  }
  /* Show the text label (nav-btn text node) */
  .nav-btn-label { display: block; }

  .class-grid { grid-template-columns: repeat(3, 1fr); }
  .page-title { font-size: 1.2rem; }
  .auth-wrap { padding: 28px 22px; }
  .step-label { display: none; }
  .step-item.active .step-label { display: inline; }
}

/* Small phones */
@media (max-width: 480px) {
  body { font-size: 13px; }
  .main-area { padding: 12px 12px 170px; }
  .card { border-radius: var(--radius-sm); }
  .btn { padding: 9px 14px; font-size: 12.5px; }
  .class-grid { grid-template-columns: repeat(2, 1fr); }
  .subject-grid { grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 10px; }
  .stat-grid { grid-template-columns: repeat(2, 1fr); gap: 8px; }
  .stat-card { padding: 14px; }
  .stat-val { font-size: 1.4rem; }
  .page-title { font-size: 1.05rem; }
  .toast { left: 12px; right: 12px; max-width: none; }
  .tbl th, .tbl td { padding: 8px 8px; font-size: 12px; }
}