:root {
  --bg: #f3f5fa;
  --bg-accent: radial-gradient(1200px 500px at 80% -10%, #e4eaff 0%, transparent 60%),
               radial-gradient(900px 420px at -10% 0%, #e9f6ef 0%, transparent 55%);
  --card: #ffffff;
  --ink: #1a2130;
  --muted: #667085;
  --line: #e4e8f1;
  --accent: #3a5bdb;
  --accent-strong: #2c46c4;
  --accent-soft: #e9eeff;
  --good: #178a4e;
  --good-soft: #e1f4e9;
  --bad: #c23b31;
  --bad-soft: #fbe7e5;
  --warn: #a8720a;
  --warn-soft: #fdf3d8;
  --shadow: 0 1px 2px rgba(16, 24, 40, 0.05), 0 6px 20px rgba(16, 24, 40, 0.06);
  --radius: 14px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f131c;
    --bg-accent: radial-gradient(1200px 500px at 80% -10%, #1b2440 0%, transparent 60%),
                 radial-gradient(900px 420px at -10% 0%, #14261d 0%, transparent 55%);
    --card: #171c29;
    --ink: #e8ebf4;
    --muted: #98a1b5;
    --line: #262d3f;
    --accent: #7c96ff;
    --accent-strong: #96acff;
    --accent-soft: #1f2847;
    --good: #46c98a;
    --good-soft: #153326;
    --bad: #f08a80;
    --bad-soft: #3a1e1c;
    --warn: #e5b45c;
    --warn-soft: #33290f;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 8px 24px rgba(0, 0, 0, 0.35);
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  background-image: var(--bg-accent);
  background-repeat: no-repeat;
  color: var(--ink);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

/* ---------------------------------------------------------------- topbar */
#topbar {
  display: flex;
  align-items: center;
  gap: 18px;
  padding: 12px 24px;
  background: color-mix(in srgb, var(--card) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 20;
}
#topbar.hidden { display: none; }
.brand { font-weight: 800; font-size: 17px; letter-spacing: -0.2px; white-space: nowrap; }
#topbar nav { display: flex; gap: 4px; flex: 1; }
#topbar nav a {
  text-decoration: none;
  color: var(--muted);
  padding: 7px 14px;
  border-radius: 10px;
  font-weight: 600;
  font-size: 14px;
  transition: background 0.15s, color 0.15s;
}
#topbar nav a:hover { color: var(--ink); }
#topbar nav a.active { background: var(--accent-soft); color: var(--accent); }
.userbox { display: flex; align-items: center; gap: 10px; color: var(--muted); font-size: 14px; }

main { max-width: 880px; margin: 0 auto; padding: 26px 18px 90px; }

/* ---------------------------------------------------------------- cards */
.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px;
  margin-bottom: 18px;
  box-shadow: var(--shadow);
}
h1 { font-size: 22px; margin: 0 0 6px; letter-spacing: -0.3px; }
h2 { font-size: 17px; margin: 0 0 12px; letter-spacing: -0.2px; }
.sub { color: var(--muted); font-size: 14px; margin: 0 0 18px; }

/* ---------------------------------------------------------------- buttons */
.btn {
  border: none;
  border-radius: 11px;
  padding: 11px 22px;
  font-size: 15px;
  font-weight: 700;
  font-family: inherit;
  cursor: pointer;
  background: var(--accent);
  color: #fff;
  box-shadow: 0 1px 2px rgba(16, 24, 40, 0.15);
  transition: background 0.15s, transform 0.08s, filter 0.15s;
}
.btn:hover { background: var(--accent-strong); filter: brightness(1.04); }
.btn:active { transform: scale(0.97); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }
.btn.ghost {
  background: transparent;
  color: var(--accent);
  border: 1.5px solid var(--line);
  box-shadow: none;
}
.btn.ghost:hover { border-color: var(--accent); background: var(--accent-soft); }
.btn.small { padding: 6px 13px; font-size: 13px; border-radius: 9px; }
.btn.full { width: 100%; }

button:focus-visible, a:focus-visible, input:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* ---------------------------------------------------------------- login */
.login-wrap { max-width: 400px; margin: 9vh auto 0; text-align: center; }
.login-wrap .brand { font-size: 28px; margin-bottom: 6px; }
.login-wrap input {
  width: 100%;
  padding: 13px 15px;
  font-size: 16px;
  font-family: inherit;
  border: 1.5px solid var(--line);
  border-radius: 11px;
  margin: 16px 0 12px;
  background: var(--card);
  color: var(--ink);
}
.login-wrap input:focus { border-color: var(--accent); outline: none; }

/* ---------------------------------------------------------------- branch picker */
.branch-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(235px, 1fr)); gap: 10px; }
.branch-item {
  display: flex;
  align-items: center;
  gap: 10px;
  border: 1.5px solid var(--line);
  border-radius: 11px;
  padding: 12px 14px;
  cursor: pointer;
  background: var(--card);
  transition: border-color 0.15s, background 0.15s;
  min-height: 48px;
}
.branch-item:hover { border-color: var(--accent); }
.branch-item:has(input:checked) { border-color: var(--accent); background: var(--accent-soft); }
.branch-item input { width: 18px; height: 18px; accent-color: var(--accent); flex-shrink: 0; }
.branch-item .bname { flex: 1; font-weight: 600; font-size: 14px; }
.branch-item .bcount { color: var(--muted); font-size: 12px; white-space: nowrap; }

.exam-options { margin-top: 18px; border-top: 1px solid var(--line); }
.optrow {
  display: flex;
  align-items: flex-start;
  gap: 11px;
  padding: 13px 2px;
  border-bottom: 1px solid var(--line);
  font-size: 14.5px;
  cursor: pointer;
}
.optrow:last-child { border-bottom: none; }
.optrow input { width: 18px; height: 18px; margin-top: 2px; accent-color: var(--accent); flex-shrink: 0; }
.hint { font-size: 13px; color: var(--muted); }

/* ---------------------------------------------------------------- exam */
.exam-bar {
  position: sticky;
  top: 62px;
  z-index: 15;
  background: color-mix(in srgb, var(--card) 92%, transparent);
  backdrop-filter: blur(10px);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 12px 18px;
  margin-bottom: 18px;
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
  box-shadow: var(--shadow);
}
.exam-bar .progress { flex: 1 1 150px; min-width: 120px; }
.meter { height: 8px; background: var(--line); border-radius: 4px; overflow: hidden; }
.meter > div { height: 100%; background: var(--accent); border-radius: 4px; width: 0; transition: width 0.25s; }
.live-score { white-space: nowrap; font-size: 14px; }

.qcard { margin-bottom: 16px; }
.qhead { display: flex; gap: 10px; align-items: center; margin-bottom: 10px; flex-wrap: wrap; }
.qnum { font-weight: 800; color: var(--accent); min-width: 30px; font-size: 16px; }
.branch-tag {
  font-size: 11.5px;
  font-weight: 700;
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 999px;
  padding: 3px 11px;
  white-space: nowrap;
}
.qtext { margin: 0 0 10px 40px; font-size: 15.5px; white-space: pre-wrap; }
.opts { margin-left: 26px; }
.opt {
  display: flex;
  gap: 11px;
  align-items: flex-start;
  border: 1.5px solid var(--line);
  border-radius: 11px;
  padding: 12px 14px;
  margin-bottom: 8px;
  cursor: pointer;
  font-size: 14.5px;
  background: var(--card);
  transition: border-color 0.15s, background 0.15s;
  min-height: 46px;
}
.opt:hover { border-color: var(--accent); }
.opt:has(input:checked) { border-color: var(--accent); background: var(--accent-soft); }
.opt input { margin-top: 3px; width: 16px; height: 16px; accent-color: var(--accent); flex-shrink: 0; }
.opt .letter { font-weight: 700; color: var(--muted); min-width: 20px; }
.opt:has(input:disabled) { cursor: default; }
.opt:has(input:disabled):hover { border-color: var(--line); }

/* ---------------------------------------------------------------- badges / review */
.score-hero { text-align: center; padding: 26px 10px 12px; }
.score-big { font-size: 54px; font-weight: 800; letter-spacing: -2px; }
.score-hero .verdict { font-size: 16px; margin-top: 2px; }
.badge {
  display: inline-block;
  border-radius: 999px;
  padding: 3px 12px;
  font-size: 12.5px;
  font-weight: 700;
}
.badge.good { background: var(--good-soft); color: var(--good); }
.badge.bad { background: var(--bad-soft); color: var(--bad); }
.badge.warn { background: var(--warn-soft); color: var(--warn); }

.table-wrap { overflow-x: auto; -webkit-overflow-scrolling: touch; }
table { width: 100%; border-collapse: collapse; font-size: 14px; }
th, td { text-align: left; padding: 10px 10px; border-bottom: 1px solid var(--line); white-space: nowrap; }
th { color: var(--muted); font-weight: 700; font-size: 11.5px; text-transform: uppercase; letter-spacing: 0.5px; }
tbody tr:last-child td { border-bottom: none; }
td.num, th.num { text-align: right; }

.review .opt.correct { border-color: var(--good); background: var(--good-soft); }
.review .opt.wrong-pick { border-color: var(--bad); background: var(--bad-soft); }
.review .opt.dim { opacity: 0.6; }
.review .opt .mark { margin-left: auto; font-size: 12px; font-weight: 700; white-space: nowrap; padding-left: 10px; }
.review .opt .mark.ok { color: var(--good); }
.review .opt .mark.no { color: var(--bad); }
.review .qcard { animation: fadein 0.25s ease; }
@keyframes fadein { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }
.opt .mark.ok, .opt .mark.no { animation: fadein 0.2s ease; }

.delta-up { color: var(--good); font-weight: 700; }
.delta-down { color: var(--bad); font-weight: 700; }
.delta-same { color: var(--muted); }

.actions { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 8px; }
.error-box { background: var(--bad-soft); color: var(--bad); border-radius: 10px; padding: 11px 15px; margin: 10px 0; font-size: 14px; }
.empty-note { color: var(--muted); text-align: center; padding: 30px 0; }

/* ---------------------------------------------------------------- mobile */
@media (max-width: 640px) {
  #topbar {
    position: static;
    flex-wrap: wrap;
    gap: 8px 12px;
    padding: 10px 14px;
  }
  .brand { font-size: 15.5px; }
  #topbar nav { order: 3; width: 100%; }
  #topbar nav a { flex: 1; text-align: center; padding: 8px 6px; }
  .userbox { margin-left: auto; font-size: 13px; }

  main { padding: 14px 12px 70px; }
  .card { padding: 16px 15px; border-radius: 12px; }
  h1 { font-size: 19px; }
  h2 { font-size: 16px; }
  .sub { font-size: 13.5px; margin-bottom: 14px; }

  .login-wrap { margin-top: 6vh; padding: 0 6px; }

  .branch-list { grid-template-columns: 1fr; gap: 8px; }

  .exam-bar {
    top: 0;
    padding: 10px 12px;
    gap: 8px 14px;
    border-radius: 12px;
  }
  .exam-bar .btn { padding: 10px 16px; font-size: 14px; }
  .exam-bar .hint { font-size: 12.5px; }

  .qtext { margin-left: 0; font-size: 15px; }
  .opts { margin-left: 0; }
  .opt { padding: 12px 13px; font-size: 14px; }
  .score-big { font-size: 44px; }
  .table-wrap { margin: 0 -15px; padding: 0 15px; }
  th, td { padding: 9px 8px; font-size: 13px; }
}