:root {
  --bg: #f4f8fd;
  --panel: #ffffff;
  --muted: #64748b;
  --text: #0f172a;
  --line: #dbe4ef;
  --primary: #2563eb;
  --primary-soft: #eef4ff;
  --shadow: 0 18px 44px rgba(15, 23, 42, 0.06);
  --radius: 24px;
}

* { box-sizing: border-box; }
body { margin: 0; font-family: "PingFang SC", "Microsoft YaHei", sans-serif; background: linear-gradient(180deg, #f5f8fd 0%, #edf3f8 100%); color: var(--text); }
a { color: inherit; text-decoration: none; }
button { cursor: pointer; border: 0; }

.app-shell { min-height: 100vh; }
.topbar { position: sticky; top: 0; z-index: 10; background: rgba(255,255,255,.96); border-bottom: 1px solid #e5ecf6; backdrop-filter: blur(10px); }
.topbar-inner, .page-wrap { width: min(1280px, calc(100vw - 48px)); margin: 0 auto; }
.topbar-inner { display: flex; align-items: center; justify-content: space-between; gap: 16px; padding: 18px 0; }
.brand { display: flex; align-items: center; gap: 14px; }
.brand-mark { width: 52px; height: 52px; border-radius: 16px; background: var(--primary); color: #fff; display: grid; place-items: center; font-weight: 700; }
.brand-title { font-size: 28px; font-weight: 700; }
.brand-sub { font-size: 12px; color: #94a3b8; letter-spacing: 1px; }
.nav { display: flex; align-items: center; gap: 10px; flex-wrap: nowrap; }
.nav a { padding: 10px 18px; border-radius: 999px; font-size: 16px; color: #475569; white-space: nowrap; }
.nav a.active { background: var(--primary-soft); color: var(--primary); font-weight: 600; }
.page-wrap { padding: 24px 0 32px; }
.hero, .card { background: var(--panel); border-radius: 32px; box-shadow: var(--shadow); }
.hero { padding: 28px; background: linear-gradient(135deg, #eaf2ff 0%, #f7faff 70%, #fff 100%); }
.hero-grid, .grid-2, .grid-3, .grid-4, .report-grid, .training-grid { display: grid; gap: 18px; }
.hero-grid { grid-template-columns: 1.15fr .85fr; }
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.report-grid { grid-template-columns: 1.1fr .9fr; }
.training-grid { grid-template-columns: 240px 1fr 320px; }
.section-title { font-size: 34px; font-weight: 700; margin: 0; }
.headline { font-size: 52px; line-height: 1.25; margin: 12px 0 0; }
.muted { color: var(--muted); }
.hero-actions, .button-row { display: flex; flex-wrap: wrap; gap: 12px; }
.btn, .btn-secondary { display: inline-flex; align-items: center; justify-content: center; padding: 12px 22px; border-radius: 999px; font-size: 16px; font-weight: 600; }
.btn { background: var(--primary); color: #fff; }
.btn-secondary { background: #fff; color: var(--primary); border: 1px solid var(--line); }
.stats, .tiles, .cards { display: grid; gap: 16px; }
.stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.stat, .tile, .mini-card, .answer-card, .ai-card, .empty, .error, .loading { border-radius: 24px; background: #fff; padding: 20px; box-shadow: var(--shadow); }
.mini-card { background: #f8fbff; }
.stat-label { font-size: 14px; color: var(--muted); }
.stat-value { margin-top: 10px; font-size: 34px; font-weight: 700; }
.two-col { display: grid; grid-template-columns: 240px 1fr; gap: 18px; }
.three-col { display: grid; grid-template-columns: 220px 1fr 320px; gap: 18px; }
.side-list { display: grid; gap: 12px; }
.side-item { padding: 16px; border-radius: 22px; background: #f8fafc; font-size: 16px; }
.side-item.active { background: var(--primary-soft); color: var(--primary); font-weight: 600; }
.list { display: grid; gap: 14px; }
.record { border-radius: 22px; background: #f8fafc; padding: 18px; }
.chip { display: inline-flex; align-items: center; padding: 8px 12px; border-radius: 999px; font-size: 13px; }
.chip.primary { background: var(--primary-soft); color: var(--primary); }
.chip.success { background: #ecfdf5; color: #166534; }
.chip.warn { background: #fff7ed; color: #c2410c; }
.chip.gray { background: #f3f4f6; color: #64748b; }
.progress { height: 12px; border-radius: 999px; background: #e2e8f0; overflow: hidden; }
.progress > span { display: block; height: 100%; background: linear-gradient(90deg, #60a5fa 0%, #2563eb 100%); }
.option { border: 1px solid var(--line); border-radius: 22px; padding: 18px 20px; display: flex; gap: 14px; align-items: center; font-size: 18px; }
.option.active { background: var(--primary-soft); color: var(--primary); border-color: var(--primary); }
.answer-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; }
.answer-cell { height: 58px; border-radius: 18px; border: 1px solid var(--line); display: grid; place-items: center; background: #fff; font-weight: 700; }
.answer-cell.active { background: var(--primary); color: #fff; border-color: var(--primary); }
.answer-cell.done { background: #eef4ff; color: var(--primary); border-color: #bfdbfe; }
.textarea, .search-input { width: 100%; border: 1px solid var(--line); border-radius: 18px; padding: 14px 16px; font: inherit; background: #fff; }
.textarea { min-height: 140px; resize: vertical; }
.table-like { display: grid; gap: 12px; }
.table-row { display: grid; grid-template-columns: 1.2fr .8fr .8fr; gap: 12px; padding: 16px; border-radius: 18px; background: #f8fafc; }
.loading, .error, .empty { text-align: center; }
.loading, .error, .empty, .card { padding: 24px; }
.app-badge { display: inline-flex; padding: 8px 12px; border-radius: 999px; background: #eef4ff; color: var(--primary); font-size: 13px; font-weight: 600; }
.toolbar { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; justify-content: space-between; }
.copy-note { font-size: 13px; color: var(--muted); }
.aigc-course-hero { background: radial-gradient(circle at 10% 10%, #dcfce7 0, transparent 28%), linear-gradient(135deg, #eef7ff 0%, #f8fbf3 58%, #ffffff 100%); }
.aigc-chapter-card { border: 1px solid #e5ecf6; }
.aigc-knowledge-card { background: linear-gradient(180deg, #ffffff 0%, #f8fbff 100%); border: 1px solid #e6eef8; }
.entitlement-card { margin-top: 16px; border-radius: 24px; padding: 18px; border: 1px solid #dbeafe; background: rgba(255, 255, 255, .72); }
.entitlement-card.blocked { border-color: #fed7aa; background: #fff7ed; }
.entitlement-card.testing { border-color: #bfdbfe; background: #eff6ff; }
.entitlement-card.active { border-color: #bbf7d0; background: #f0fdf4; }
.entitlement-title { margin: 10px 0 6px; font-size: 20px; font-weight: 700; color: #9a3412; }
.tutor-panel:empty { display: none; }
.tutor-shell { display: grid; grid-template-columns: minmax(0, 1.55fr) minmax(320px, 0.9fr); gap: 18px; align-items: start; }
.tutor-main { display: grid; gap: 18px; align-content: start; }
.tutor-tools .side-item { width: 100%; border: 0; text-align: left; display: grid; gap: 6px; }
.tutor-conversation { min-height: 680px; }
.tutor-thread { display: grid; gap: 16px; min-height: 270px; max-height: 540px; overflow: auto; padding: 2px; }
.tutor-message { display: flex; flex-direction: column; gap: 7px; max-width: 88%; }
.tutor-message.student { justify-self: end; align-items: flex-end; }
.tutor-message.assistant { justify-self: start; }
.tutor-role { font-size: 13px; color: var(--muted); font-weight: 600; }
.tutor-bubble { padding: 14px 16px; border-radius: 18px; white-space: pre-wrap; line-height: 1.7; background: #f1f5f9; }
.tutor-message.student .tutor-bubble { background: var(--primary); color: #fff; }
.tutor-feedback .btn-secondary { padding: 7px 13px; font-size: 13px; }
.tutor-compose { border-top: 1px solid var(--line); margin-top: 18px; padding-top: 18px; }
.tutor-compose .textarea { min-height: 100px; }
.tutor-upload-label { position: relative; overflow: hidden; }
.tutor-upload-label input { opacity: 0; position: absolute; inset: 0; cursor: pointer; }
.tutor-images { display: flex; flex-wrap: wrap; gap: 10px; align-items: flex-start; }
.tutor-images img { display: block; width: 92px; height: 92px; object-fit: cover; border-radius: 14px; border: 1px solid var(--line); }
.tutor-images > div { display: grid; gap: 5px; font-size: 12px; }
.tutor-notice .ai-card { box-shadow: none; border: 1px solid #dbeafe; }
.tutor-risk { background: #fff7ed; color: #9a3412; line-height: 1.7; }

@media (max-width: 1199px) {
  .hero-grid, .report-grid, .three-col, .training-grid { grid-template-columns: 1fr; }
  .tutor-shell { grid-template-columns: 1fr; }
  .tutor-sidebar, .tutor-tools { position: static; }
  .two-col { grid-template-columns: 1fr; }
  .grid-4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 767px) {
  .topbar-inner, .page-wrap { width: min(100vw - 24px, 1280px); }
  .nav { display: none; }
  .headline { font-size: 38px; }
  .section-title { font-size: 28px; }
  .grid-4, .grid-3, .grid-2, .stats { grid-template-columns: 1fr; }
  .answer-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}