:root {
  --color-background: #f8fbff;
  --color-surface: #ffffff;
  --color-surface-soft: #f1f6fb;
  --color-text-primary: #102033;
  --color-text-secondary: #526173;
  --color-border: #dbe7f3;
  --color-border-strong: #bfd4ea;
  --color-accent: #2563eb;
  --color-accent-soft: #e6f0ff;
  --color-success: #047857;
  --color-warning: #b45309;
  --color-danger: #b91c1c;
  --radius-md: 12px;
  --radius-lg: 16px;
  --shadow-card: 0 10px 30px rgba(15, 23, 42, 0.06);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
html, body { margin: 0; min-height: 100%; background: var(--color-background); color: var(--color-text-primary); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; }
a { color: inherit; text-decoration: none; }
button, input { font: inherit; }
.page-shell { width: min(1120px, calc(100% - 32px)); margin: 0 auto; padding: 32px 0 64px; }
.hero { display: grid; gap: 20px; padding: 40px; border: 1px solid var(--color-border); border-radius: 24px; background: linear-gradient(135deg, #ffffff, #eef6ff); box-shadow: var(--shadow-card); }
.compact-hero { padding: 32px; }
.eyebrow { color: var(--color-accent); font-size: 14px; font-weight: 800; letter-spacing: .04em; }
.hero h1 { max-width: 820px; margin: 0; font-size: clamp(32px, 5vw, 56px); line-height: 1.08; }
.hero p, .lead { max-width: 760px; margin: 0; color: var(--color-text-secondary); font-size: 17px; line-height: 1.8; }
.action-row { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }
.button { display: inline-flex; min-height: 44px; align-items: center; justify-content: center; border-radius: 999px; padding: 0 18px; border: 1px solid var(--color-border); background: var(--color-surface); color: var(--color-text-primary); font-weight: 800; cursor: pointer; }
.button.primary { color: white; background: var(--color-accent); border-color: var(--color-accent); }
.button:disabled { cursor: not-allowed; opacity: .45; }
.small-button { min-height: 34px; padding: 0 12px; font-size: 13px; }
.section-block { margin-top: 24px; }
.section-heading-row, .section-heading { display: flex; align-items: flex-end; justify-content: space-between; gap: 20px; margin-bottom: 16px; }
.section-heading-row h2, .section-heading h2 { margin: 4px 0 0; font-size: 28px; }
.section-heading-row p, .section-heading p { max-width: 520px; margin: 0; color: var(--color-text-secondary); line-height: 1.7; }
.card-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin-top: 24px; }
.card-grid.two-column { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.card { border: 1px solid var(--color-border); border-radius: var(--radius-lg); background: var(--color-surface); padding: 20px; box-shadow: var(--shadow-card); }
.card h2, .card h3 { margin: 0 0 8px; }
.card p { margin: 0; color: var(--color-text-secondary); line-height: 1.7; }
.card-title-row, .card-topline { display: flex; align-items: flex-start; justify-content: space-between; gap: 12px; }
.practice-card { display: grid; gap: 14px; align-content: start; }
.badge { display: inline-flex; min-height: 28px; align-items: center; border-radius: 999px; border: 1px solid var(--color-border); background: #eef6ff; color: var(--color-accent); padding: 0 10px; font-size: 12px; font-weight: 900; letter-spacing: 0.02em; white-space: nowrap; }
.badge.muted { color: var(--color-text-secondary); background: var(--color-surface-soft); }
.success-badge { color: #047857; background: #ecfdf5; border-color: #a7f3d0; }
.warning-badge { color: #b45309; background: #fffbeb; border-color: #fde68a; }
.danger-badge { color: var(--color-danger); background: #fff1f2; border-color: #fecdd3; }
.muted-text, .small-text { color: var(--color-text-secondary); font-size: 14px; }
.choice-list { display: grid; gap: 10px; padding: 0; margin: 16px 0 0; list-style: none; }
.choice-item, .choice-button { display: flex; width: 100%; gap: 12px; align-items: flex-start; padding: 14px 16px; border: 1px solid var(--color-border); border-radius: var(--radius-md); background: var(--color-surface-soft); color: var(--color-text-primary); text-align: left; }
.choice-button { cursor: pointer; }
.choice-button.selected-choice { border-color: var(--color-accent); background: var(--color-accent-soft); }
.choice-button.correct-choice { border-color: #a7f3d0; background: #ecfdf5; }
.choice-button.wrong-choice { border-color: #fecdd3; background: #fff1f2; }
.choice-label { display: inline-flex; min-width: 28px; height: 28px; align-items: center; justify-content: center; border-radius: 999px; color: var(--color-accent); background: white; font-weight: 900; }
.question-stack, .practice-stack, .dashboard-stack { display: grid; gap: 18px; margin-top: 24px; }
.question-card { display: grid; gap: 14px; }
.question-meta-row { display: flex; flex-wrap: wrap; gap: 8px; }
.question-body { font-size: 18px; }
.explanation-box, .explanation-panel { border: 1px solid var(--color-border); border-radius: var(--radius-md); background: #f8fbff; padding: 14px 16px; }
.explanation-box summary { cursor: pointer; font-weight: 800; }
.explanation-box p, .explanation-panel p { margin-top: 10px; }
.notice-card { margin-top: 24px; }
.notice-text { margin: 0; color: var(--color-text-secondary); line-height: 1.7; }
.warning-text { color: #92400e; }
.error-text { color: var(--color-danger); font-weight: 800; }
.field-label { display: grid; gap: 8px; color: var(--color-text-primary); font-weight: 800; }
.text-input { min-height: 44px; border: 1px solid var(--color-border); border-radius: var(--radius-md); background: var(--color-surface); color: var(--color-text-primary); padding: 0 14px; width: min(100%, 360px); }
.result-summary, .compact-summary, .review-filter-row { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.metric-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin-top: 24px; }
.metric-card { display: grid; gap: 8px; }
.metric-card span { color: var(--color-text-secondary); font-size: 14px; font-weight: 700; }
.metric-card strong { font-size: 32px; }
.dashboard-list { display: grid; gap: 12px; margin-top: 16px; }
.dashboard-list-row { display: flex; align-items: flex-start; justify-content: space-between; gap: 16px; }
.review-action-row, .question-action-row { display: flex; flex-wrap: wrap; gap: 8px; }
.sticky-submit-card { position: sticky; bottom: 16px; z-index: 5; margin-top: 24px; display: grid; gap: 14px; }
.filter-notice { display: flex; flex-wrap: wrap; gap: 0.75rem; align-items: center; justify-content: space-between; }
.question-navigator-card { display: grid; gap: 16px; }
.question-navigator-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(118px, 1fr)); gap: 8px; }
.question-nav-link { display: grid; gap: 4px; min-height: 72px; padding: 10px 12px; border: 1px solid var(--color-border); border-radius: var(--radius-md); background: var(--color-surface); color: var(--color-text-primary); text-decoration: none; }
.question-nav-link:hover, .question-nav-link:focus-visible { border-color: var(--color-accent); box-shadow: 0 0 0 3px rgba(37, 99, 235, .12); outline: none; }
.question-nav-link span { width: fit-content; color: var(--color-text-secondary); font-size: 12px; font-weight: 800; }
.question-nav-muted { opacity: .62; }
.question-nav-diff { border-color: #fde68a; background: #fffbeb; }
.question-navigator-toolbar { display: grid; gap: 10px; }
.question-navigator-legend { display: flex; flex-wrap: wrap; gap: 8px 12px; color: var(--color-text-secondary); font-size: 12px; font-weight: 700; }
.preview-ribbon { margin: 0 0 16px; padding: 12px 16px; border: 1px solid #fde68a; background: #fffbeb; color: #92400e; border-radius: var(--radius-md); font-weight: 800; }
.top-nav { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; justify-content: space-between; margin-bottom: 16px; }
.top-nav-links { display: flex; flex-wrap: wrap; gap: 8px; }
@media (max-width: 760px) {
  .page-shell { width: min(100% - 24px, 1120px); padding-top: 20px; }
  .hero { padding: 24px; border-radius: 20px; }
  .card-grid, .card-grid.two-column, .metric-grid { grid-template-columns: 1fr; }
  .section-heading-row, .section-heading, .dashboard-list-row { align-items: flex-start; flex-direction: column; }
  .sticky-submit-card { bottom: 8px; }
  .button { flex: 1 1 auto; }
}