/* Web study surfaces. Loaded after the existing themes and account styles.
   Theme ownership and the existing responsive layouts stay with their sources.
   A narrow desktop preview must receive the same surfaces as a wide browser. */
@media screen {
  :root {
    --study-paper: color-mix(in srgb, var(--brand-surface, #fff) 96%, #f4ead8);
    --study-ground: color-mix(in srgb, var(--brand-bg) 72%, #f3eee3);
    --study-edge: color-mix(in srgb, var(--brand-primary) 23%, var(--brand-surface, #fff));
    --study-edge-soft: color-mix(in srgb, var(--brand-primary) 13%, var(--brand-surface, #fff));
    --study-shadow: 0 4px 0 var(--study-edge-soft), 0 12px 28px color-mix(in srgb, var(--brand-ink) 7%, transparent);
    --study-shadow-small: 0 3px 0 var(--study-edge-soft), 0 5px 12px color-mix(in srgb, var(--brand-ink) 4%, transparent);
    --study-primary-shadow: 0 4px 0 var(--brand-hover), 0 7px 16px color-mix(in srgb, var(--brand-primary) 13%, transparent);
  }

  body {
    background-color: var(--study-ground);
    background-image: radial-gradient(ellipse at 50% 0, var(--brand-surface, #fff), transparent 65%);
    color: var(--brand-ink);
    font-size: 16px;
    line-height: 1.75;
    -webkit-font-smoothing: antialiased;
  }

  body > header {
    margin-top: 16px;
    border: 1px solid var(--study-edge);
    border-bottom-width: 3px;
    border-radius: 20px;
    background: var(--study-paper);
    box-shadow: 0 6px 20px color-mix(in srgb, var(--brand-ink) 4%, transparent);
    padding-block: 18px;
  }

  body[data-session="active"] > header {
    width: calc(100% - 2 * var(--workspace-gutter));
    max-width: calc(1760px - 2 * var(--workspace-gutter));
    padding-inline: 24px;
  }

  .brand-icon { width: 48px; height: 48px; }
  .header-actions { gap: 12px; }
  #identity { font-size: 13px; font-weight: 600; }
  #themeSelect { min-height: 44px; border-radius: 12px; font-weight: 600; }

  .hero { padding: 60px 16px 42px; gap: 40px; }
  h1 { font-size: clamp(48px, 4.2vw, 62px); font-weight: 750; letter-spacing: -.04em; line-height: 1.3; }
  h2 { font-size: 28px; font-weight: 750; line-height: 1.45; }
  h3 { font-size: 21px; font-weight: 700; }
  .intro { font-size: 16px; line-height: 2; }
  .eyebrow { font-size: 11px; letter-spacing: .15em; color: var(--brand-primary); }
  .hero-art { width: 288px; margin-right: 24px; }
  .hero-art .math-orb {
    width: 252px;
    border-radius: 50%;
    background: radial-gradient(circle, var(--brand-tint), transparent 70%);
    filter: drop-shadow(0 8px 8px color-mix(in srgb, var(--brand-primary) 9%, transparent));
  }
  .hero-art span { font-size: 12px; letter-spacing: .08em; }

  .panel, .access-card, .membership-plan, .membership-order, .globe-progress {
    border: 1px solid var(--study-edge);
    border-radius: 22px;
    background: var(--study-paper);
    box-shadow: var(--study-shadow);
  }
  .panel { padding: 32px; }
  .muted { font-size: 13px; }
  .small { font-size: 12px; }
  label { font-size: 14px; font-weight: 600; color: var(--brand-ink); }
  .primary, .secondary, .tabs button, .domain, .node, .knowledge-link {
    transition: background-color 160ms ease, border-color 160ms ease, box-shadow 160ms ease, transform 160ms ease;
  }
  .primary {
    min-height: 48px;
    padding: 12px 24px;
    border: 1px solid var(--brand-primary);
    border-radius: 13px;
    font-size: 14px;
    font-weight: 700;
    box-shadow: var(--study-primary-shadow);
  }
  .primary:hover:not(:disabled) { transform: translateY(-1px); }
  .primary:active:not(:disabled) { transform: translateY(3px); box-shadow: 0 1px 0 var(--brand-hover); }
  .secondary {
    min-height: 46px;
    border: 1px solid var(--study-edge);
    border-radius: 12px;
    background: var(--brand-surface, #fff);
    color: var(--brand-ink);
    font-size: 13px;
    font-weight: 600;
    box-shadow: 0 2px 0 var(--study-edge-soft);
  }
  .secondary:hover:not(:disabled) { background: var(--brand-tint); border-color: var(--brand-primary); }
  .secondary:active:not(:disabled) { transform: translateY(1px); box-shadow: none; }
  .header-actions .secondary { min-height: 42px; font-size: 12px; }
  button:disabled { box-shadow: none; transform: none; }
  input:not([type="checkbox"]):not([type="range"]):not([type="file"]), textarea, select {
    border-color: var(--study-edge);
    border-radius: 12px;
    box-shadow: inset 0 2px 3px color-mix(in srgb, var(--brand-ink) 4%, transparent);
  }
  input:focus, textarea:focus, select:focus {
    border-color: var(--brand-primary);
    box-shadow: 0 0 0 4px color-mix(in srgb, var(--brand-primary) 12%, transparent);
  }
  button:focus-visible, a:focus-visible, summary:focus-visible, canvas:focus-visible {
    outline: 3px solid var(--brand-secondary);
    outline-offset: 4px;
  }

  .login { max-width: 500px; padding: 36px 40px; border-top: 5px solid var(--brand-primary); }
  .login h2 { font-size: 28px; }
  .login .auth-intro { font-size: 14px; }
  .login input { min-height: 50px; }
  .auth-tabs { padding: 6px; border: 1px solid var(--study-edge-soft); border-radius: 14px; background: var(--brand-tint); }
  .login .auth-tabs button { border-radius: 10px; font-weight: 700; }
  .login .auth-tabs button.active { box-shadow: 0 2px 0 var(--study-edge-soft), 0 3px 8px color-mix(in srgb, var(--brand-ink) 6%, transparent); }

  body[data-session="active"] .tabs {
    padding: 10px;
    margin: 24px 0 28px;
    gap: 10px;
    border: 1px solid var(--study-edge);
    border-radius: 18px;
    background: var(--study-paper);
    box-shadow: var(--study-shadow-small);
  }
  .tabs button {
    min-height: 48px;
    padding: 11px 20px;
    border: 1px solid transparent;
    border-radius: 12px;
    font-size: 12px;
    font-weight: 600;
    /* Switch the fill and label together so a new white label never flashes
       against the old white surface during keyboard or pointer navigation. */
    transition: box-shadow 160ms ease, transform 160ms ease;
  }
  .tabs span { font-size: 15px; margin-left: 10px; }
  .tabs button:hover:not(.active) { background: var(--brand-tint); color: var(--brand-primary); }
  .tabs button.active { box-shadow: 0 3px 0 var(--brand-hover), 0 5px 12px color-mix(in srgb, var(--brand-primary) 12%, transparent); }
  .section-heading { margin-bottom: 24px; padding: 4px 4px 4px 16px; border-left: 4px solid var(--brand-primary); }
  .section-heading .eyebrow { margin-bottom: 5px; }
  .section-heading > .muted { font-size: 13px; }

  .domain-list { gap: 18px; margin-bottom: 28px; }
  body[data-session="active"] .domain {
    padding: 20px;
    gap: 16px;
    min-height: 104px;
    border: 1px solid var(--study-edge);
    border-radius: 18px;
    background: var(--study-paper);
    box-shadow: var(--study-shadow-small);
  }
  .domain .symbol {
    display: grid;
    place-items: center;
    flex-shrink: 0;
    width: 52px;
    height: 52px;
    border: 1px solid var(--study-edge-soft);
    border-radius: 16px;
    background: var(--brand-tint);
    font-size: 30px;
  }
  .domain strong { font-size: 16px; font-weight: 750; }
  .domain small { font-size: 12px; }
  .domain .arrow { color: var(--brand-primary); }
  body[data-session="active"] .domain:hover { border-color: var(--brand-primary); transform: translateY(-2px); }
  body[data-session="active"] .domain.active {
    background: var(--brand-tint);
    border-color: var(--brand-primary);
    box-shadow: inset 0 3px 0 var(--brand-primary), 0 4px 0 var(--study-edge), 0 8px 20px color-mix(in srgb, var(--brand-primary) 8%, transparent);
  }
  .domain.active .symbol { background: var(--brand-primary); color: #fff; border-color: var(--brand-primary); }

  #questionPicker {
    padding: 20px 24px;
    margin-block: 20px 28px;
    border: 1px solid var(--study-edge);
    border-radius: 18px;
    background: var(--study-paper);
    box-shadow: var(--study-shadow-small);
  }
  .difficulty-heading label { font-size: 15px; }
  .difficulty-heading output, .difficulty-ends { font-size: 13px; }
  .difficulty-track input[type="range"] { box-shadow: none; }
  .difficulty-track input::-webkit-slider-runnable-track { height: 8px; }
  .difficulty-track input::-webkit-slider-thumb { width: 26px; height: 26px; margin-top: -9px; border-width: 4px; }

  body[data-session="active"] .question { padding: 0 36px 36px; border-top: 5px solid var(--brand-primary); }
  .question-top {
    margin: 0 -36px 28px;
    padding: 18px 36px;
    border-bottom: 1px solid var(--study-edge);
    border-radius: 16px 16px 0 0;
    background: var(--brand-tint);
    font-size: 13px;
    gap: 16px;
    flex-wrap: wrap;
  }
  .question-top #progress { color: var(--brand-primary); font-weight: 700; }
  .math-content { font-size: 18px; line-height: 2; }
  #stem { padding: 4px 4px 12px; }
  #answerForm {
    margin-top: 32px;
    padding: 24px;
    border: 1px solid var(--study-edge);
    border-radius: 18px;
    background: var(--brand-surface, #fff);
    box-shadow: inset 0 3px 0 var(--study-edge-soft);
  }
  #answerForm > label { font-size: 16px; margin-bottom: 14px; }
  #answer {
    border: 1px solid var(--study-edge-soft);
    border-radius: 12px;
    padding: 12px 16px;
    min-height: 174px;
    background-color: var(--study-paper);
    background-image: repeating-linear-gradient(transparent 0, transparent 31px, var(--study-edge-soft) 31px, var(--study-edge-soft) 32px);
    background-origin: content-box;
    background-clip: padding-box;
    background-position: 0 12px;
    font-size: 16px;
    line-height: 32px;
    box-shadow: inset 0 2px 5px color-mix(in srgb, var(--brand-ink) 3%, transparent);
  }
  #answer:focus { border-color: var(--brand-primary); box-shadow: 0 0 0 4px color-mix(in srgb, var(--brand-primary) 10%, transparent); }
  #answer::placeholder { color: var(--brand-muted); }
  .actions { gap: 14px; margin-top: 22px; }
  .upload-trigger { border-radius: 12px; border-color: var(--study-edge); font-size: 13px; }
  .handwriting-panel > summary { font-size: 14px; font-weight: 600; }

  .teaching-panel { padding: 28px; border-color: var(--study-edge); border-radius: 20px; background: var(--brand-tint); }
  .teaching-heading h3 { font-size: 22px; }
  .knowledge-link { padding: 11px 14px; border-color: var(--study-edge); border-radius: 12px; box-shadow: 0 2px 0 var(--study-edge-soft); }
  .knowledge-link:hover { border-color: var(--brand-primary); }
  .hint-step { padding: 12px 18px; border-left-width: 4px; border-radius: 0 12px 12px 0; }
  .solution-step, .method-card, .rubric-card, .solution-conclusion {
    border-radius: 16px;
    padding: 22px 24px;
    box-shadow: 0 3px 0 color-mix(in srgb, var(--brand-ink) 5%, transparent);
  }
  .solution-step { border-color: var(--study-edge); }
  .step-label { font-size: 13px; }
  .step-label > span { width: 36px; height: 36px; border-radius: 11px; border: 1px solid var(--study-edge); font-weight: 750; }
  .step-content { font-size: 16px; }
  .step-reason { font-size: 14px; border: 1px solid #e7dcc3; border-radius: 12px; }
  .exam-context { border-color: var(--study-edge); border-radius: 18px; }
  .coordinate-metrics strong { font-weight: 750; }

  .atlas-frame { border-color: var(--study-edge); border-width: 1px; border-radius: 22px; box-shadow: var(--study-shadow); }
  .globe-progress { padding: 24px 28px; }
  .globe-progress strong { font-size: 34px; font-weight: 750; }
  .globe-progress progress { height: 10px; }
  .graph-layout { gap: 24px; }
  .graph-layout aside { padding: 22px; }
  #nodeSearch { font-size: 14px; }
  .node { margin: 3px 0; padding: 12px; border-radius: 11px; font-size: 14px; }
  .node small { font-size: 11px; }
  .node.selected { background: var(--brand-tint); box-shadow: inset 3px 0 0 var(--brand-primary); color: var(--brand-primary); font-weight: 650; }
  #nodeDetail h3 { font-size: 24px; }
  #nodeDetail p { font-size: 14px; }
  .node-item-group .compact-item { padding: 12px 14px; border-color: var(--study-edge); border-radius: 12px; background: var(--brand-surface, #fff); box-shadow: 0 2px 0 var(--study-edge-soft); }
  .globe-tools { gap: 10px; }

  .access-card { padding: 32px; border-top: 5px solid var(--study-edge); }
  .access-card.member { border-top-color: var(--brand-primary); background: var(--brand-tint); }
  .access-card .access-price { font-weight: 750; }
  .membership-plan { padding: 28px; border-top: 4px solid var(--study-edge); }
  .account-status { padding: 20px; border: 1px solid var(--study-edge-soft); background: var(--brand-tint); border-radius: 20px; }
  .account-access-label { border: 1px solid var(--study-edge); background: var(--brand-surface, #fff); }
  .account-recent-works > summary { font-size: 15px; }
  dialog { border-color: var(--study-edge); border-radius: 22px; padding: 32px; background: var(--study-paper); box-shadow: 0 24px 80px color-mix(in srgb, var(--brand-ink) 24%, transparent); }
  dialog::backdrop { background: color-mix(in srgb, var(--brand-ink) 35%, transparent); }
  footer { padding: 26px 8px 8px; font-size: 12px; border-color: var(--study-edge); }
}

@media screen and (max-width: 800px) {
  body { font-size: 15px; }
  body > header { width: calc(100% - 32px); margin-top: 12px; padding: 14px 16px; border-radius: 16px; }
  body[data-session="active"] > header { padding: 14px 16px; }
  .brand-icon { width: 40px; height: 40px; }
  .header-actions { gap: 8px; }
  #themeSelect { min-height: 40px; }
  .hero { padding: 32px 0 26px; gap: 24px; }
  h1 { font-size: clamp(34px, 5.8vw, 46px); }
  h2 { font-size: 24px; }
  h3 { font-size: 19px; }
  .intro { font-size: 14px; }
  .hero-art { width: 210px; margin-right: 0; }
  .hero-art .math-orb { width: 200px; }
  .panel { padding: 22px; border-radius: 18px; }
  .login { padding: 28px 24px; margin-top: 16px; }
  .login h2 { font-size: 26px; }
  body[data-session="active"] .tabs { padding: 8px; gap: 6px; margin: 18px 0 22px; border-radius: 16px; }
  .tabs button { min-height: 42px; padding: 8px 10px; font-size: 11px; }
  .tabs span { font-size: 13px; margin-left: 5px; }
  .section-heading { padding-left: 12px; margin-bottom: 20px; }
  .domain-list { gap: 12px; margin-bottom: 20px; }
  body[data-session="active"] .domain { min-height: 90px; padding: 16px; gap: 12px; border-radius: 16px; }
  .domain .symbol { width: 44px; height: 44px; border-radius: 13px; font-size: 27px; }
  .domain strong { font-size: 15px; }
  #questionPicker { padding: 16px 18px; margin-block: 16px 24px; }
  body[data-session="active"] .question { padding: 0 20px 24px; }
  .question-top { margin-inline: -20px; padding: 14px 20px; font-size: 12px; }
  .math-content { font-size: 16px; }
  #answerForm { padding: 18px; margin-top: 24px; }
  #answerForm > label { font-size: 15px; }
  #answer { min-height: 160px; padding-inline: 12px; font-size: 15px; }
  .teaching-panel { padding: 20px; }
  .teaching-heading h3 { font-size: 20px; }
  .solution-step, .method-card, .rubric-card, .solution-conclusion { padding: 18px; }
  .globe-progress { padding: 20px; }
  .globe-progress strong { font-size: 28px; }
  .graph-layout aside { padding: 20px; }
  .access-card, .membership-plan { padding: 24px; }
  .account-status { padding: 16px; }
  dialog { padding: 24px; }
}

@media screen and (prefers-reduced-motion: reduce) {
  .primary, .secondary, .tabs button, .domain, .node, .knowledge-link { transition: none; }
  .primary:hover:not(:disabled), .primary:active:not(:disabled), .secondary:active:not(:disabled), body[data-session="active"] .domain:hover { transform: none; }
}