:root {
  --sky-0: #e8f6ff;
  --sky-1: #c8ebff;
  --sky-2: #7dd3fc;
  --sky-3: #38bdf8;
  --sky-4: #0ea5e9;
  --sky-5: #0369a1;
  --ink: #0f3a55;
  --muted: #4b6f86;
  --card: rgba(255, 255, 255, 0.86);
  --ok: #059669;
  --bad: #dc2626;
  --warn: #d97706;
  --radius: 16px;
}

* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  color: var(--ink);
  background: #bfe9ff;
  padding-bottom: env(safe-area-inset-bottom);
}

.sky-bg {
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(1200px 500px at 10% -10%, #ffffff 0%, transparent 55%),
    radial-gradient(900px 420px at 110% 10%, #7dd3fc 0%, transparent 50%),
    linear-gradient(180deg, #d7f3ff 0%, #87ceeb 48%, #5ec4f2 100%);
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  position: sticky;
  top: 0;
  background: rgba(232, 246, 255, 0.82);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(14, 165, 233, 0.18);
  z-index: 10;
}
.brand {
  font-weight: 800;
  color: var(--sky-5);
  text-decoration: none;
  letter-spacing: 0.4px;
}
.nav { display: flex; gap: 12px; flex-wrap: wrap; }
.nav a {
  color: var(--sky-5);
  text-decoration: none;
  font-size: 14px;
  font-weight: 600;
}

.page {
  max-width: 820px;
  margin: 0 auto;
  padding: 16px 14px 40px;
}

.card {
  background: var(--card);
  border: 1px solid rgba(14, 165, 233, 0.18);
  border-radius: var(--radius);
  box-shadow: 0 10px 30px rgba(3, 105, 161, 0.08);
  padding: 18px;
  margin-bottom: 14px;
}

h1, h2 { margin: 0 0 10px; font-size: 22px; }
.h-sub { color: var(--muted); margin: 0 0 16px; font-size: 14px; }

.flash-list { display: grid; gap: 8px; margin-bottom: 12px; }
.flash {
  border-radius: 12px;
  padding: 10px 12px;
  font-size: 14px;
}
.flash.success { background: #d1fae5; color: #065f46; }
.flash.danger { background: #fee2e2; color: #991b1b; }
.flash.warning { background: #fef3c7; color: #92400e; }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 16px;
  border: 0;
  border-radius: 12px;
  background: var(--sky-4);
  color: #fff;
  font-weight: 700;
  text-decoration: none;
  cursor: pointer;
  width: 100%;
}
.btn:disabled { opacity: 0.55; cursor: not-allowed; }
.btn.secondary { background: #ffffff; color: var(--sky-5); border: 1px solid var(--sky-3); }
.btn.ghost { background: transparent; color: var(--sky-5); border: 1px dashed var(--sky-3); }
.btn.danger { background: #ef4444; }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.stack { display: grid; gap: 10px; }

label { display: block; font-size: 13px; color: var(--muted); margin-bottom: 6px; }
input[type=text], input[type=password], input[type=file], select {
  width: 100%;
  min-height: 44px;
  border-radius: 12px;
  border: 1px solid #b6e3f8;
  padding: 10px 12px;
  background: #fff;
  font-size: 16px;
}

.bank-chip {
  display: inline-block;
  background: #e0f2fe;
  color: var(--sky-5);
  border-radius: 999px;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 700;
}

.mode-card { text-decoration: none; color: inherit; display: block; }
.mode-card h3 { margin: 0 0 6px; font-size: 18px; }
.mode-card p { margin: 0; color: var(--muted); font-size: 13px; }

.choice {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  padding: 12px;
  border: 1px solid #cfefff;
  border-radius: 12px;
  background: #fff;
  margin-bottom: 8px;
  cursor: pointer;
}
.choice input { margin-top: 3px; }
.choice.correct { border-color: #34d399; background: #ecfdf5; }
.choice.wrong { border-color: #f87171; background: #fef2f2; }
.q-meta { color: var(--muted); font-size: 13px; margin-bottom: 8px; }
.explain {
  margin-top: 12px;
  padding: 12px;
  border-radius: 12px;
  background: #f0f9ff;
  color: #075985;
  white-space: pre-wrap;
}
.progress {
  height: 8px;
  background: #dbeafe;
  border-radius: 99px;
  overflow: hidden;
  margin: 8px 0 14px;
}
.progress > span {
  display: block;
  height: 100%;
  background: var(--sky-4);
}
.q-item { scroll-margin-top: 70px; }
.toast {
  position: fixed;
  left: 50%;
  bottom: 24px;
  transform: translateX(-50%);
  background: #0f3a55;
  color: #fff;
  padding: 10px 14px;
  border-radius: 999px;
  font-size: 14px;
  display: none;
  z-index: 20;
}
.stat { display: flex; gap: 10px; flex-wrap: wrap; }
.stat b { font-size: 22px; color: var(--sky-5); }
.count-row { display: flex; justify-content: space-between; font-size: 14px; padding: 6px 0; }
@media (min-width: 720px) {
  .btn { width: auto; min-width: 140px; }
}