:root {
  --brand: #4d5bc4;
  --brand-deep: #3545a8;
  --brand-soft: #edf0ff;
  --accent: #1d9bff;
  --page: #f3f5f8;
  --surface: #fff;
  --text: #1c2940;
  --muted: #718096;
  --line: #e1e6ef;
  --shadow: 0 10px 28px rgba(49, 66, 122, .08);
  --radius: 5px;
}

body { background: var(--page); }
.topbar { background: var(--brand); }
.topbar::after { opacity: .16; background: linear-gradient(116deg, transparent 8%, #a6baff 8% 17%, transparent 17% 36%, #8ca6ff 36% 50%, transparent 50%); }
.brand-mark { border-color: rgba(255,255,255,.7); border-radius: 50%; color: #fff; transform: none; }
.brand-lockup p { color: rgba(255,255,255,.74); }
.top-action, .icon-button { border-color: rgba(255,255,255,.38); border-radius: 4px; background: rgba(30, 42, 131, .25); }
.top-action.primary { border-color: rgba(255,255,255,.38); background: rgba(255,255,255,.14); }
.icon-button { border-radius: 4px; }
.sidebar { background: var(--brand); box-shadow: 0 8px 18px rgba(49, 66, 122, .16); }
.avatar-large { border-radius: 50%; color: #fff; background: #8d99dc; }
.nav-item { color: rgba(255,255,255,.87); }
.nav-item span { color: #fff; }
.nav-item:hover, .nav-item.active { background: rgba(255,255,255,.14); }
.nav-item.active { border-left: 0; }
.search-box { border-radius: 4px; background: var(--surface); box-shadow: var(--shadow); }
.search-box > span { color: var(--brand); }
.search-box button { border-left: 1px solid var(--line); border-radius: 0; margin-right: 0; color: var(--brand-deep); background: var(--brand-soft); }
.category-strip { background: var(--surface); box-shadow: var(--shadow); }
.category-item:hover, .category-item.active { color: var(--text); background: var(--brand-soft); }
.category-item:hover span, .category-item.active span { color: var(--muted); }
.content-panel, .rail-panel, .purchase-bar { border-color: var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.section-dot { border-radius: 50%; background: var(--accent); transform: none; }
.course-card { border-color: var(--line); border-radius: 4px; background: #fff; box-shadow: none; }
.course-card:hover { border-color: #a9b7ed; box-shadow: 0 10px 24px rgba(69, 83, 166, .15); }
.cover span { font-family: Georgia, serif; font-weight: 400; }
.purchase-bar { background: var(--brand); }
.purchase-bar:hover { background: var(--brand-deep); }
.recommend-cover { border-radius: 3px; background: #6d7dcb; }
.recommend-item em { color: #f19727; }
.topic-card { border-radius: 4px; color: var(--brand-deep); background: var(--brand-soft); }
.topic-card:nth-child(2n) { color: #126c76; background: #effafa; }