/* desk: shared styles; retain order with the other component sheets. */
@layer components {
/* ---------- 學習工作桌：視覺層次與起始引導 ---------- */
.topbar { min-height: 72px; padding: 12px 24px; gap: 16px; }
.brand { gap: 10px; flex-shrink: 0; }
.brand-mark { width: 36px; height: 36px; display: grid; place-items: center; color: var(--ink); background: var(--panel-2); border: 1px solid var(--border); border-radius: 9px; }
.brand-mark img { width: 30px; height: 30px; }
.brand-caption { color: var(--muted); font-size: 11px; border-left: 1px solid var(--border); margin-left: 6px; padding-left: 16px; }
.topbar-actions { gap: 4px; }
.topbar .btn { min-height: 40px; }
#pick-btn { margin-left: 8px; box-shadow: 0 3px 8px rgba(41, 39, 37, .08); }
.layout { padding: 18px; padding-top: 16px; }
.viewer-pane { border: 1px solid var(--border); border-radius: 12px; overflow: hidden; }
.chat-pane { border: 1px solid var(--border); border-radius: 12px; }
.viewer { background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='22' height='22'%3E%3Ccircle cx='1' cy='1' r='.65' fill='%23B8ACA0' opacity='.4'/%3E%3C/svg%3E"); background-size: 22px 22px; }
.viewer:has(.viewer-pages) { background-image: none; }
.pane-splitter { --splitter-size: 14px; }
.pane-splitter::after { border-radius: 4px; }
.pane-splitter.vertical::after { top: calc(50% - 20px); bottom: auto; height: 40px; width: 3px; }
.pane-splitter.horizontal::after { left: calc(50% - 20px); right: auto; width: 40px; height: 3px; }
.drop-hint { width: 100%; max-width: 720px; margin: auto; align-items: center; text-align: center; padding: 24px 20px; gap: 0; }
.desk-eyebrow { display: flex; align-items: center; gap: 8px; font-size: 11px; font-weight: 600;   }
.desk-eyebrow > span { width: 5px; height: 5px; background: var(--accent); border-radius: 50%; }
.paper-study { width: 280px; height: 205px; position: relative; margin: 24px 0 20px; flex-shrink: 0; }
.study-sheet { position: absolute; width: 202px; height: 183px; left: 38px; top: 6px; border: 1px solid var(--border-strong); border-radius: 3px; }
.sheet-back { background: var(--panel-2); transform: rotate(-12deg) translate(-10px, -1px); }
.sheet-front { padding: 19px 20px; background: var(--panel); transform: rotate(5deg); box-shadow: 0 12px 22px rgba(41, 39, 37, .09); }
.sheet-heading { font-family: Georgia, serif; font-size: 7px; letter-spacing: .1em; display: flex; justify-content: space-between; color: var(--muted); }
.sheet-rule { margin-top: 8px; border-top: 1px solid var(--border); }
.sheet-formula { font-family: Georgia, serif; font-size: 21px; color: var(--text); padding: 11px 0 6px; }
.sheet-lines i { display: block; width: 80%; height: 3px; background: var(--border); margin: 5px 0; }
.sheet-lines i:last-child { width: 58%; }
.sheet-question { height: 67px; margin-top: 9px; position: relative; border: 1px solid var(--accent); border-radius: 5px; background: var(--accent-soft); color: var(--accent); }
.sheet-question svg { width: 100%; height: 100%; }
.sheet-dot { position: absolute; top: -7px; left: -7px; width: 18px; height: 18px; background: var(--ink); color: var(--on-ink); border-radius: 50%; font-size: 10px; display: grid; place-items: center; }
.sheet-annotation { position: absolute; right: -30px; bottom: 2px; color: var(--accent);  padding: 3px 8px; border: 1px solid var(--border); border-radius: 4px; font-size: 10px; transform: rotate(-5deg); }
.study-tag { position: absolute; bottom: -3px; left: 10px;   padding: 7px 13px; font-size: 11px;  transform: rotate(-5deg); box-shadow: 0 4px 12px rgba(41, 39, 37, .1); }
.drop-hint p.desk-description { font-family: var(--font-ui);  font-weight: 400; color: var(--muted);  line-height: 1.85; }
.desk-actions { display: flex; flex-direction: column; align-items: center; gap: 9px; }
.desk-upload { min-height: 48px; gap: 12px; padding: 13px 22px; border-radius: 9px; box-shadow: 0 5px 14px rgba(41, 39, 37, .12); }
.desk-upload > span { margin-left: 10px; font-size: 18px; font-weight: 400; }
.drop-caption { font-size: 11px; color: var(--muted); }
.desk-steps { display: flex; justify-content: center; list-style: none;   padding: 0; color: var(--muted); font-size: 11px; }
.desk-steps li { display: flex; align-items: center; gap: 7px; }
.desk-steps li > span { font-family: Georgia, serif; color: var(--accent); font-size: 12px; font-style: italic; }
.desk-resume { font: inherit; font-size: 12px; color: var(--accent); cursor: pointer; border: 0; border-top: 1px solid var(--border); background: none; padding: 15px 24px 0; min-height: 44px; }
.desk-resume small { display: block; font-size: 10px; color: var(--muted); margin-top: 3px; }
.workspace-label {  display: flex; justify-content: space-between; align-items: center; gap: 12px;  font-weight: 600; }
.workspace-label > span:first-child { display: flex; align-items: center; gap: 9px; }
.workspace-dot { width: 6px; height: 6px; border-radius: 50%; background: var(--accent); }
.workspace-caption {  color: var(--muted); font-weight: 400; }
.chat-head .field > span { font-size: 11px; }
.chat-head select { background: var(--panel-2); border-color: transparent; border-radius: 7px; }
.chat-head .field.grow { flex-basis: 100px; }
.chat-head .answer-font-field { flex: 0 0 auto; }
.answer-font-controls { display: flex; align-items: center; gap: 7px; }
.answer-font-step { display: grid; place-items: center; width: 32px; height: 32px; padding: 0; border: 1px solid var(--border); border-radius: 7px; background: var(--panel-2); color: var(--text); font: inherit; font-size: 16px; cursor: pointer; }
.answer-font-step:disabled { opacity: .35; cursor: default; }
.answer-font-step:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }
#answer-font-value { min-width: 34px; text-align: center; color: var(--muted); font-size: 11px; font-variant-numeric: tabular-nums; }
@media (hover: hover) { .answer-font-step:not(:disabled):hover { border-color: var(--accent); color: var(--accent); } }
.chat-head .star-btn { width: 28px; padding: 6px 0; }
.chat-model { font-size: 10px; color: var(--muted); }
.messages:empty::before { content: none; }
.messages:empty { display: none; }
.chat-welcome { display: none; flex: 1; min-height: 0; overflow: auto; flex-direction: column; align-items: flex-start; justify-content: safe center; padding: clamp(22px, 3vw, 48px); }
.messages:empty + .chat-welcome { display: flex; }
.welcome-symbol { display: grid; place-items: center;   margin-bottom: 22px; background: var(--panel-2);  border: 1px solid var(--border);  }
.welcome-eyebrow { font-family: var(--font-serif); font-size: 22px; letter-spacing: .02em; color: var(--text); margin-bottom: 18px; line-height: 1.6; }
.chat-welcome p { font-size: 14px; line-height: 1.9; color: var(--muted); margin: 0; }
.welcome-note { margin-top: 28px; padding-top: 14px; border-top: 1px solid var(--border); width: 100%;   }
.welcome-note > span { margin-right: 8px; }
.ask-form { margin: 12px 16px 16px; padding: 10px 14px; padding-bottom: calc(10px + env(safe-area-inset-bottom)); gap: 6px; border-radius: 12px;  }
.ask-form:focus-within { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.math-chat-editor { min-height: 38px; }
.math-input-help { font-size: 10px; }
.formula-mobile { display: none; }
.ask-actions { border-top: 0; padding-top: 0; flex-wrap: nowrap; }
.ask-actions .math-input-help { display: block; flex: 1; min-width: 0; margin: 0 auto 0 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.ask-actions > .muted { font-size: 10px; }
#send-btn { width: 40px; height: 40px; padding: 0; border-radius: 9px; }
.msg.user .msg-text { border-radius: 12px 12px 3px 12px; }
.toolbar { padding: 10px 14px; }
.zoom { flex-basis: 100%; margin-left: 0; gap: 4px; }
.zoom button { border-radius: 6px; padding: 0 8px; min-height: 32px; font-size: 12px; }
#zoom-in, #zoom-out { width: 32px; }
#close-file { margin-left: auto; color: var(--muted); }
.settings, .library, .admin-dialog { box-shadow: 0 24px 80px rgba(41, 39, 37, .18); }
.desk-resume:focus-visible, .desk-upload:focus-visible { outline: 2px solid var(--accent); outline-offset: 4px; }
@media (hover: hover) {
  .desk-upload:hover { background: var(--accent); border-color: var(--accent); }
  .desk-resume:hover { text-decoration: underline; text-underline-offset: 4px; }
}
@media (min-width: 1100px) and (min-height: 800px) {
  .paper-study { margin-top: 46px; margin-bottom: 40px; transform: scale(1.1); }
}
@media (max-width: 1250px) { .brand-caption { display: none; } }
@media (max-height: 760px) and (min-width: 900px) and (orientation: landscape) {
  .drop-hint { padding-top: 14px; padding-bottom: 14px; }
  .paper-study { transform: scale(.75); height: 140px; margin: 10px 0; }
  .drop-hint p.desk-description { margin: 10px 0 15px; }
  .desk-steps { margin: 12px 0; }
  .desk-resume { padding-top: 10px; }
  .welcome-symbol { width: 44px; height: 44px; min-height: 44px; margin-bottom: 12px; border-radius: 13px 13px 13px 3px; }
  .chat-welcome { padding-top: 20px; padding-bottom: 20px; }
  .welcome-note { margin-top: 16px; }
}
@media (max-height: 700px) and (min-width: 900px) and (orientation: landscape) {
  .paper-study { height: 130px; transform: scale(.68); transform-origin: top center; margin-bottom: 6px; }
  .welcome-symbol, .welcome-eyebrow, .welcome-note { display: none; }
}
@media (max-width: 899.98px), (orientation: portrait) and (max-width: 1099.98px) {
  .layout { padding: 10px; padding-top: 6px; }
  .drop-hint { display: grid; grid-template-columns: 1fr auto; align-content: center; align-items: center; text-align: left; padding: 18px 22px; gap: 12px 22px; max-width: 750px; }
  .desk-eyebrow { grid-column: 1; font-size: 10px; }
  .paper-study { grid-column: 2; grid-row: 1 / 4; width: 220px; height: 200px; margin: 0; transform: scale(.85); }
  .drop-hint p.desk-description { margin: 0; font-size: 12px; grid-column: 1; }
  .desk-actions { grid-column: 1; align-items: flex-start; }
  .desk-upload { min-height: 44px; font-size: 12px; padding: 10px 14px; gap: 8px; }
  .desk-steps { grid-column: 1 / -1; justify-content: flex-start; margin: 2px 0; }
  .desk-resume { grid-column: 1 / -1; text-align: left; padding: 10px 0 0; }
  .desk-resume small { display: inline; margin-left: 10px; }
  .workspace-label { padding: 12px 16px 8px; }
  .chat-head { padding: 0 16px 10px; }
  .chat-head .field.grow { flex: 1 1 140px; }
  .chat-welcome { padding: 15px 22px; }
  .welcome-symbol, .welcome-eyebrow, .welcome-note { display: none; }
  .chat-welcome p { font-size: 11px; }
  .ask-form { margin: 8px 12px 12px; }
  .math-chat-editor { min-height: 38px; }
}
@media (max-width: 639.98px) {
  .topbar { min-height: 60px; padding: 8px 12px; padding-top: calc(8px + env(safe-area-inset-top)); }
  .brand { gap: 7px; }
  .brand-mark { width: 29px; height: 29px; border-radius: 8px; }
  .brand-mark img { width: 25px; height: 25px; }
  .brand-name { font-size: 13px; letter-spacing: 0; }
  .topbar-actions { gap: 2px; }
  #pick-btn { margin-left: 0; padding: 8px 10px; font-size: 12px; }
  .viewer-pane, .chat-pane { border-radius: 12px; }
  .drop-hint { display: flex; align-items: flex-start; text-align: left; padding: 18px; gap: 0; }
  .paper-study { display: none; }
  .drop-hint p.desk-description { margin-bottom: 14px; font-size: 12px; }
  .desktop-break { display: none; }
  .desk-actions { flex-direction: row; flex-wrap: wrap; gap: 7px 12px; }
  .drop-caption { font-size: 10px; }
  .desk-steps { margin: 14px 0 10px; gap: 18px; font-size: 10px; }
  .desk-resume { width: 100%; font-size: 11px; }
  .desk-resume small { display: block; margin: 3px 0 0; }
  .workspace-caption { display: none; }
  .chat-welcome { padding: 6px 16px; }
  .welcome-secondary { display: none; }
  .chat-head { gap: 5px; }
  .chat-head .field > span { font-size: 10px; }
  .chat-head select { padding: 6px 7px; min-height: 34px; font-size: 14px; }
  .chat-model { font-size: 10px; }
  .ask-actions { padding: 0; }
  .math-input-help { font-size: 10px; }
  .formula-desktop { display: none; }
  .formula-mobile { display: inline; }
  .ask-form { gap: 6px; padding: 10px 12px; padding-bottom: calc(10px + env(safe-area-inset-bottom)); max-height: min(260px, max(160px, calc(100% - 130px))); }
  .ask-actions { bottom: -10px; }
  #send-btn, #attach-btn, #chat-phone-upload-btn { min-width: 44px; min-height: 44px; }
  .settings, .library, .admin-dialog { border-radius: 0; }
}
@media (prefers-reduced-motion: no-preference) {
  .paper-study { animation: study-arrive 220ms ease-out both; }
  @keyframes study-arrive { from { opacity: 0; translate: 0 8px; } to { opacity: 1; translate: 0 0; } }
}

/* 選取講解 → 帶著引用追問；不改動原生文字選取與複製。 */
.quote-selection-action { position: fixed; z-index: 70; min-height: 40px; padding: 9px 14px; border: 1px solid var(--border-strong); border-radius: 9px; background: var(--panel); color: var(--accent); font: inherit; font-size: 12px; font-weight: 600; box-shadow: var(--shadow); cursor: pointer; max-width: calc(100vw - 16px); }
.quote-selection-action:hover { background: var(--panel-2); }
.quote-selection-action:focus-visible, .quote-reply-remove:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }
.quote-reply-preview { display: flex; flex-shrink: 0; gap: 10px; align-items: flex-start; background: var(--panel-2); border-left: 3px solid var(--accent); border-radius: 4px 8px 8px 4px; padding: 8px 10px; }
.quote-reply-passage { min-width: 0; flex: 1; }
.quote-reply-label { font-size: 10px; color: var(--accent); font-weight: 600; }
.quote-reply-passage blockquote { margin: 3px 0 0; padding: 0; border: 0; color: var(--muted); font-size: 12px; line-height: 1.65; white-space: pre-wrap; overflow-wrap: anywhere; max-height: 80px; overflow: auto; }
.quote-reply-remove { display: grid; place-items: center; flex-shrink: 0; width: 32px; height: 32px; padding: 0; background: transparent; color: var(--muted); border: 0; border-radius: 6px; font: inherit; font-size: 20px; cursor: pointer; }
.quote-reply-remove:hover { background: var(--border); color: var(--text); }
.reply-jump { cursor: pointer; }
.reply-jump:focus-visible { outline: 2px solid var(--accent); outline-offset: 4px; border-radius: 4px; }
.reply-jump-hint { display: block; margin-top: 8px; color: var(--accent); font-size: 12px; }
.reply-jump:hover .reply-jump-hint { text-decoration: underline; }
.quoted-message { white-space: normal; }
.quoted-passage { border-left: 3px solid var(--border-strong); padding: 0 0 0 10px; margin-bottom: 10px; }
.quoted-label { font-size: 12px; color: var(--muted); }
summary.quoted-label { cursor: pointer; min-height: 32px; }
.quoted-body { font-size: 13px; color: var(--muted); overflow-wrap: anywhere; }
.quoted-message .markdown p, .quote-reply-passage .markdown p { margin: 5px 0; }
.quoted-message .katex-display, .quote-reply-passage .katex-display { overflow-x: auto; overflow-y: hidden; max-width: 100%; }
.quote-reply-passage blockquote.markdown { white-space: normal; }
.answer-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; margin: 10px 0 5px; font-family: var(--font-sans); }
.answer-action, .answer-version { font: inherit; font-size: 12px;   border: 1px solid var(--border); border-radius: 6px; min-height: 32px; padding: 5px 9px; }
.answer-action { cursor: pointer; }
.answer-action:disabled { opacity: .5; cursor: default; }
.answer-action:focus-visible, .answer-version:focus-visible, summary.quoted-label:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.messages:not([data-mode="full"]) .answer-action.is-verify { display: none; }
/* 批改結果：與學習進度同一套語意色（理解＝accent、卡住＝danger） */
.grading-verdict { display: inline-flex; align-items: center; gap: 6px; align-self: flex-start; width: fit-content; margin: 0 0 8px; padding: 3px 10px 3px 8px; font-family: var(--font-sans); font-size: 12px; font-weight: 600; line-height: 1.5; border: 1px solid currentColor; border-radius: 999px; background: var(--panel); }
.grading-verdict::before { content: ''; width: 7px; height: 7px; border-radius: 50%; background: currentColor; }
.grading-verdict.is-correct { color: var(--accent); background: var(--accent-soft); }
.grading-verdict.is-wrong { color: var(--danger); background: var(--danger-soft); }
.grading-verdict.is-unclear { color: var(--muted); }
.verdict-actions { display: flex; flex-wrap: wrap; gap: 8px; margin: 10px 0 2px; }
.verdict-action { font: inherit; font-size: 13px; color: var(--accent); background: var(--accent-soft); border: 1px solid var(--accent); border-radius: var(--radius-sm); min-height: 34px; padding: 5px 12px; cursor: pointer; transition: background var(--dur-fast) var(--ease), color var(--dur-fast) var(--ease); }
.verdict-action:hover:not(:disabled) { background: var(--accent); color: var(--on-ink); }
.verdict-action:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.verdict-action:disabled { cursor: default; }
.verdict-action.is-done { background: transparent; border-color: var(--border); color: var(--muted); }
@media (pointer: coarse) { .verdict-action { min-height: 44px; } }
/* 快捷追問：輸入框上方一排，空間不夠時橫向捲動而不是換行撐高 */
.quick-asks { display: flex; flex-wrap: nowrap; gap: 6px; overflow-x: auto; overscroll-behavior-x: contain; scrollbar-width: none; margin: -2px -2px 0; padding: 2px; scroll-padding-inline: 2px; }
.quick-asks::-webkit-scrollbar { display: none; }
.quick-ask { flex: none; font: inherit; font-size: 12px; line-height: 1.2; color: var(--muted); background: transparent; border: 1px solid var(--border); border-radius: 999px; min-height: 30px; padding: 5px 11px; cursor: pointer; white-space: nowrap; transition: color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease), background var(--dur-fast) var(--ease); }
.quick-ask:hover { color: var(--accent); border-color: var(--accent); background: var(--accent-soft); }
.quick-ask:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
@media (pointer: coarse) {
  .quick-ask, .hint-more-btn { min-height: 44px; padding-inline: 14px; }
  /* 手機打字時鍵盤已佔掉空間，先收起快捷追問，留給輸入框與對話 */
  .ask-form:has(.math-chat-editor:focus, textarea:focus) .quick-asks { display: none; }
}
.study-note-title { color: var(--accent); font-size: 13px; font-weight: 600; margin-bottom: 10px; border-bottom: 1px solid var(--border); padding-bottom: 8px; }
@media (pointer: coarse) { .answer-action, .answer-version { min-height: 44px; } }
.msg.model.reply-source-highlight { outline: 2px solid var(--accent); outline-offset: 4px; border-radius: 6px; background: var(--panel-2); }
@media (pointer: coarse) { .quote-selection-action { min-height: 44px; } .quote-reply-remove { width: 44px; height: 44px; } }

/* ---------- 匯出筆記：列印 ---------- */
.print-notes {
  display: none;
}

@media print {
  /* 只印 #print-notes，強制淺色（不管目前是深色模式） */
  html,
  body {
    background: #fff !important;
    color: #000 !important;
    height: auto !important;
    overflow: visible !important;
  }

  body > *:not(#print-notes) {
    display: none !important;
  }

  .print-notes {
    display: block;
    background: #fff;
    color: #000;
    font-size: 12pt;
    line-height: 1.6;
  }

  .print-notes h1 {
    font-size: 20pt;
    margin: 0 0 4pt;
  }

  .print-notes .print-meta {
    color: #444;
    font-size: 10pt;
    margin: 0 0 14pt;
  }

  .print-notes .print-section {
    margin-bottom: 18pt;
  }

  .print-notes h2 {
    font-size: 15pt;
    margin: 14pt 0 6pt;
    padding-bottom: 3pt;
    border-bottom: 1px solid #888;
    break-after: avoid;
  }

  .print-notes .print-thumb {
    display: block;
    max-width: 100%;
    max-height: 240pt;
    margin: 6pt 0;
    border: 1px solid #bbb;
    break-inside: avoid;
  }

  .print-notes .print-user {
    margin: 8pt 0;
    padding: 4pt 10pt;
    border-left: 3px solid #888;
    color: #333;
    background: none;
  }

  .print-notes .print-answer,
  .print-notes .print-answer * {
    color: #000;
    background: transparent;
  }

  .print-notes .katex-display {
    break-inside: avoid;
  }
}

/* 尋書與學習進度：延續紙感藏書的安靜層次 */
.library-tools { display:grid; grid-template-columns:minmax(180px,1fr) auto auto; gap:18px; margin:26px 0 16px; align-items:end; }
.library-tools .field { display:flex; flex-direction:column; align-items:stretch; gap:8px; margin:0; }
.library-tools .field > span { font-size:10px; letter-spacing:.12em; font-weight:500; }
.library-tools input, .library-tools select { min-height:44px; width:100%; border-radius:9px; background:var(--panel-2); border-color:transparent; transition:border-color var(--dur), background var(--dur); }
.library-tools input { padding-left:16px; }
.library-tools input:focus, .library-tools select:focus { background:var(--panel); border-color:var(--accent); box-shadow:0 0 0 3px var(--accent-soft); }
.library-learning-note { display:flex; align-items:center; flex-wrap:wrap; gap:6px 12px; border-left:2px solid var(--border-strong); padding:3px 0 3px 12px; }
.library-learning-note > span { font-size:12px; color:var(--accent); white-space:nowrap; }
.library-learning-note p { flex:1; font-size:11px; color:var(--muted); line-height:1.7; margin:0; min-width:200px; }
.library-learning-note button { margin-left:auto; }
.book-subjects { display:flex; flex-wrap:wrap; gap:4px; margin:0 0 8px; }
.book-subject-tag { color:var(--accent); border:1px solid var(--border); padding:3px 7px; border-radius:4px; font-size:10px; line-height:1.4; overflow-wrap:anywhere; }
.book-progress { display:grid; grid-template-columns:1fr 1fr; gap:5px 8px; margin:8px 0 12px; }
.learning-badge { display:flex; align-items:center; gap:5px; font-size:10px; color:var(--muted); white-space:nowrap; font-variant-numeric:tabular-nums; }
.learning-badge::before { content:''; flex:none; width:5px; height:5px; border-radius:50%; background:var(--border-strong); }
.learning-badge[data-status='understood'][data-active='true'] { color:var(--accent); }
.learning-badge[data-status='understood'][data-active='true']::before { background:var(--accent); }
.learning-badge[data-status='stuck'][data-active='true']::before { background:var(--danger); }
.learning-badge[data-status='review'][data-active='true']::before { background:var(--text); box-shadow:0 0 0 2px var(--panel), 0 0 0 3px var(--border-strong); }
.learning-unknown { grid-column:1/-1; font-size:10px; color:var(--muted); }
.book-actions { flex-wrap:wrap; gap:6px 12px; border-top:1px solid var(--border); padding-top:8px; }
.book-actions .book-status { flex-basis:100%; }
.book-edit:hover { color:var(--accent); }
.learning-field select[data-status='understood'] { color:var(--accent); box-shadow:inset 0 -2px var(--accent); }
.learning-field select[data-status='stuck'] { box-shadow:inset 0 -2px var(--danger); }
.learning-field select[data-status='review'] { box-shadow:inset 0 -2px var(--border-strong); }
.library-metadata-dialog { width:min(460px, calc(100vw - 32px)); border:1px solid var(--border); border-radius:18px; padding:28px; background:var(--panel); color:var(--text); box-shadow:var(--shadow); }
.library-metadata-dialog h2 { font-family:Georgia,'Noto Serif TC',serif; font-size:26px; font-weight:400; margin:0 0 8px; }
.metadata-source { font-size:11px; color:var(--muted); margin:0 0 26px; overflow-wrap:anywhere; }
.library-metadata-dialog .field { display:flex; flex-direction:column; align-items:stretch; gap:9px; margin:18px 0; font-size:12px; }
.library-metadata-dialog input { width:100%; min-height:44px; }
.library-metadata-actions { display:flex; justify-content:flex-end; gap:10px; margin-top:28px; padding-top:18px; border-top:1px solid var(--border); }
.library-metadata-dialog::backdrop { background:var(--backdrop); }
@media (max-width:600px) { .library-tools { grid-template-columns:1fr 1fr; gap:14px; margin-top:22px; } .library-tools .grow { grid-column:1/-1; } .learning-field { max-width:160px; } .library-learning-note p { flex-basis:100%; } }

/* ---------- 暖紙與炭墨：全站共用的閱讀節奏 ---------- */
.btn { font-weight: 500; letter-spacing: .015em; }
.btn:not(.ghost):not(:disabled):hover { background: #403B37; border-color: #403B37; }
.topbar .btn.ghost { color: var(--muted); }
.topbar .btn.ghost:hover { color: var(--text); }
.brand-name { letter-spacing: .02em; }
.desk-title { font: 500 clamp(25px, 2.5vw, 36px)/1.5 var(--font-serif); letter-spacing: .035em; color: var(--text); margin: 0; }
.drop-hint p.desk-description { font-size: 14px; margin: 12px 0 22px; }
.study-tag { background: var(--panel); color: var(--text); border: 1px solid var(--border); border-radius: 5px; }
.sheet-annotation { background: var(--panel); }
.desk-eyebrow { color: var(--muted); letter-spacing: .08em; }
.desk-steps { gap: 24px; margin: 22px 0 18px; }
.desk-reader-link { font-size: 12px; font-weight: 400; min-height: 44px; }
.desk-phone-upload { font-size: 13px; color: var(--muted); }
.workspace-label { padding: 20px 22px 14px; font-size: 14px; letter-spacing: .025em; }
.workspace-caption { font-size: 11px; }
.chat-head { padding: 0 22px 16px; gap: 8px 12px; }
.chat-head .field > span, .chat-model, #answer-font-value { font-size: 12px; }
.messages { padding: 24px; scrollbar-gutter: stable; }
.msg-text.markdown { line-height: 1.9; }
.msg-text.markdown h1, .msg-text.markdown h2, .msg-text.markdown h3 { letter-spacing: .015em; }
.msg-text.markdown blockquote { border-left: 2px solid var(--accent); background: var(--accent-soft); border-radius: 0 6px 6px 0; }
.msg.user { border-color: transparent; border-radius: 12px 12px 3px 12px; }
.answer-action, .answer-version { background: transparent; color: var(--muted); }
.answer-action:hover { background: var(--panel-2); color: var(--text); border-color: var(--border-strong); }
.welcome-symbol { width: 48px; height: 48px; border-radius: 12px; color: var(--muted); }
.welcome-symbol img { width: 30px; height: 30px; }
.welcome-note { color: var(--muted); font-size: 12px; }
.ask-form { background: var(--panel); border-color: var(--border-strong); box-shadow: none; }
.math-input-help, .ask-actions > .muted { font-size: 11px; }
.math-chat-editor:focus-visible { outline: none; }
.settings, .library, .admin-dialog, .phone-upload-dialog { border-color: var(--border); }
:where(button, a, input, textarea, select, [contenteditable=true]):focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }
@media (min-width: 1100px) { .topbar { flex-wrap: nowrap; } .topbar-actions { flex-wrap: nowrap; } }
@media (max-width: 1599px) { .brand-caption { display: none; } .topbar { gap: 12px; padding-inline: 18px; } }
@media (min-width: 1100px) and (max-width: 1399px) {
  .topbar-actions > .btn.ghost > .btn-text { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
  .topbar-actions > .btn.ghost { min-width: 40px; padding-inline: 10px; }
}
@media (max-height: 800px) and (min-width: 900px) {
  .paper-study { margin: 8px 0; transform: scale(.72); height: 145px; }
  .desk-title { font-size: 28px; }
  .drop-hint p.desk-description { margin: 8px 0 14px; }
  .desk-steps { margin: 14px 0 10px; }
}
@media (max-width: 899.98px), (orientation: portrait) and (max-width: 1099.98px) {
  .desk-title { grid-column: 1; font-size: 25px; }
  .paper-study { grid-row: 1 / 5; }
  .workspace-label { padding: 12px 16px 10px; }
  .chat-head { padding: 0 16px 12px; }
  .messages { padding: 18px; }
}
@media (max-width: 639.98px) {
  .topbar { padding-inline: max(12px, env(safe-area-inset-left)); }
  .desk-title { font-size: 22px; line-height: 1.5; }
  .drop-hint p.desk-description { font-size: 12px; margin: 0; }
  .drop-hint { gap: 8px; }
  .paper-study { display: none; }
  .desk-eyebrow { font-size: 10px; }
  .desk-steps { margin: 8px 0; font-size: 11px; }
  .chat-head .field > span, .chat-model { font-size: 11px; }
  .chat-pane { position: relative; }
  .chat-model { position: absolute; top: 14px; right: 16px; max-width: 48%; font-size: 10px; }
  .chat-head .learning-field { flex: 1 1 auto; }
  .chat-head .learning-field > span { font-size: 0; }
  .chat-head .learning-field > span::after { content: var(--ui-progress, "進度"); font-size: 11px; }
  .chat-head .answer-font-field > span { display: none; }
  .chat-head #learning-status { min-width: 86px; }
  .desk-actions { flex-direction: column; align-items: flex-start; }
  .chat-welcome { padding: 10px 16px; }
  .workspace-label { font-size: 13px; }
  .desk-reader-link { font-size: 11px; }
  .messages { padding: 16px; }
  .topbar .btn, .answer-font-step, .answer-action, .answer-version, .star-btn, .zoom button, .quote-reply-remove { min-height: 44px; }
  .answer-font-step, .star-btn, #zoom-in, #zoom-out { min-width: 44px; }
  #send-btn, #attach-btn, #chat-phone-upload-btn { min-height: 44px; min-width: 44px; }
}
@media (prefers-reduced-motion: reduce) { .paper-study, .study-sheet { animation: none; } }

/* On short phones, reserve room for the controls and composer before the PDF. */
@media (max-width: 639.98px) and (max-height: 740px) {
  .viewer-pane { flex-shrink: 1; }
  .chat-pane { min-height: 310px; }
  .chat-welcome { padding-block: 6px; }
}

/* Generated diagrams remain legible in both themes and narrow chat panels. */
.answer-diagram { margin: 1rem 0; padding: 12px; background: #fff; border: 1px solid var(--border, #dbe3de); border-radius: 12px; overflow: hidden; }
.answer-diagram img { display: block; width: 100%; max-width: 720px; height: auto; margin: auto; }
.diagram-error { color: var(--muted); font-size: .9em; }

/* Copy changes only; retain the existing responsive layout. */


/* 回答工具列：最新一則顯示常用動作，其餘收進「⋯」；較早的回答淡一點，滑過或聚焦才清楚 */
.answer-actions:not(.is-latest) { opacity: .72; transition: opacity var(--dur) var(--ease); }
.msg.model:hover .answer-actions, .answer-actions:focus-within { opacity: 1; }
.answer-action.is-primary { color: var(--accent); border-color: var(--accent); background: var(--accent-soft); }
.answer-more { position: relative; }
.answer-more > summary { list-style: none; display: inline-flex; align-items: center; justify-content: center; min-width: 32px; letter-spacing: .08em; user-select: none; }
.answer-more > summary::-webkit-details-marker { display: none; }
.answer-more[open] > summary { background: var(--panel-2); color: var(--text); border-color: var(--border-strong); }
.answer-menu { position: absolute; z-index: 6; bottom: calc(100% + 4px); left: 0; display: flex; flex-direction: column; min-width: 148px; padding: 4px; background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius-sm); box-shadow: var(--shadow); animation: answer-menu-in var(--dur) var(--ease); }
.answer-menu .answer-action { border-color: transparent; border-radius: 5px; text-align: left; color: var(--text); }
.answer-menu .answer-action:hover, .answer-menu .answer-action:focus-visible { background: var(--panel-2); border-color: transparent; }
@keyframes answer-menu-in { from { opacity: 0; transform: translateY(3px); } }
.answer-versions { display: inline-flex; align-items: center; gap: 2px; min-height: 32px; padding: 0 2px; border: 1px solid var(--border); border-radius: 999px; font-size: 12px; color: var(--muted); }
.answer-version-step { width: 28px; height: 28px; border: 0; border-radius: 50%; background: transparent; color: inherit; font: inherit; font-size: 15px; line-height: 1; cursor: pointer; }
.answer-version-step:hover:not(:disabled) { background: var(--panel-2); color: var(--text); }
.answer-version-step:disabled { opacity: .35; cursor: default; }
.answer-version-step:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
.answer-version-label { padding: 0 4px; font-variant-numeric: tabular-nums; white-space: nowrap; }
@media (pointer: coarse) { .answer-version-step { width: 40px; height: 40px; } .answer-versions { min-height: 44px; } .answer-more > summary { min-width: 44px; } }
/* 完整解答的「最終答案」：一眼找得到的結論卡片 */
.msg-text.markdown .final-answer { margin: 1.2em 0; padding: 14px 16px; border: 1px solid color-mix(in srgb, var(--accent) 36%, var(--border)); border-radius: var(--radius); background: var(--accent-soft); }
.msg-text.markdown .final-answer > :is(h2, h3, h4):first-child { display: flex; align-items: center; gap: 7px; margin: 0 0 .55em; font-family: var(--font-sans); font-size: 12px; font-weight: 600; letter-spacing: .08em; color: var(--accent); }
.msg-text.markdown .final-answer > :is(h2, h3, h4):first-child::before { content: ''; width: 6px; height: 6px; border-radius: 50%; background: currentColor; }
.msg-text.markdown .final-answer > :last-child { margin-bottom: 0; }
.msg-text.markdown > .final-answer:last-child { margin-bottom: 0; }
/* 重新產生時先淡化舊版本 */
.msg-text.markdown.is-previous { opacity: .42; filter: saturate(.6); transition: opacity var(--dur) var(--ease); }
.cursor { margin-left: 1px; }
/* 公式與表格太寬時在自己的區塊內橫向捲動，不撐破對話也不被裁掉 */
.msg-text.markdown .katex-display { overflow-x: auto; overflow-y: hidden; max-width: 100%; padding-block: 2px; }
.msg-text.markdown table { display: block; width: max-content; max-width: 100%; overflow-x: auto; }
/* 往上捲讀時的「最新回答」按鈕 */
.jump-latest { position: absolute; left: 50%; bottom: 14px; z-index: 3; transform: translateX(-50%); display: inline-flex; align-items: center; gap: 7px; min-height: 34px; padding: 6px 14px; font: inherit; font-family: var(--font-sans); font-size: 12px; color: var(--text); background: var(--panel); border: 1px solid var(--border-strong); border-radius: 999px; box-shadow: var(--shadow); cursor: pointer; animation: jump-latest-in var(--dur) var(--ease); }
.jump-latest[hidden] { display: none; }
.jump-latest:hover { border-color: var(--accent); color: var(--accent); }
.jump-latest:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.jump-latest-dot { display: none; width: 6px; height: 6px; border-radius: 50%; background: var(--accent); }
.jump-latest.is-live .jump-latest-dot { display: block; animation: soft-blink 1.2s ease-in-out infinite; }
@keyframes jump-latest-in { from { opacity: 0; transform: translate(-50%, 6px); } }
@media (pointer: coarse) { .jump-latest { min-height: 44px; } }
/* 講解面板標頭：題目、模式、進度、錯題星號與顯示設定排成一列；字體與模型收進「Aa」 */
.workspace-label { padding: 16px 22px 10px; }
.chat-head { padding: 0 22px 12px; gap: 8px; }
.chat-head .conv-field { order: 1; flex: 1 1 160px; }
.chat-head .mode-field { order: 2; }
.chat-head .learning-field { order: 3; }
.chat-head .star-btn { order: 4; }
.chat-head .usage-remaining { order: 5; }
.chat-view-menu { order: 6; position: relative; }
.chat-head :is(.conv-field, .mode-field) > span { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
.chat-head .learning-field > span { font-size: 0; }
.chat-head .learning-field > span::after { content: var(--ui-progress, "進度"); font-size: 11px; }
.chat-view-toggle { list-style: none; display: grid; place-items: center; width: 34px; height: 34px; border: 1px solid transparent; border-radius: 7px; color: var(--muted); font-family: var(--font-serif); font-size: 14px; cursor: pointer; user-select: none; transition: background var(--dur-fast) var(--ease), color var(--dur-fast) var(--ease); }
.chat-view-toggle::-webkit-details-marker { display: none; }
.chat-view-toggle:hover, .chat-view-menu[open] > .chat-view-toggle { background: var(--panel-2); color: var(--text); }
.chat-view-toggle:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.chat-view-panel { position: absolute; right: 0; top: calc(100% + 6px); z-index: 20; display: flex; flex-direction: column; align-items: flex-start; gap: 10px; min-width: 210px; padding: 12px 14px; background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius-sm); box-shadow: var(--shadow); animation: answer-menu-in var(--dur) var(--ease); }
.chat-view-panel .answer-font-field > span { display: inline; font-size: 12px; }
.chat-view-panel .chat-model { position: static; margin: 0; max-width: 260px; font-size: 12px; white-space: normal; }
@media (pointer: coarse) { .chat-view-toggle { width: 44px; height: 44px; } }
/* 手機：標題列只是裝飾，收起來；標頭直接貼齊面板上緣 */
@media (max-width: 639.98px) {
  .workspace-label { display: none; }
  .chat-head { flex-wrap: nowrap; padding-top: 10px; }
  .chat-head .conv-field { flex: 1 1 auto; }
  .chat-view-panel .learning-field > span { font-size: 12px; }
  .chat-view-panel .learning-field > span::after { content: none; }
}
/* 手機輸入時收起標頭，把高度留給講解與輸入框 */
@media (max-width: 899.98px) {
  .chat-pane:has(.math-chat-editor:focus) :is(.workspace-label, .chat-head) { display: none; }
}
/* 輸入框上方的短暫提示、螢幕閱讀器狀態 */
.composer-hint { margin: 0 0 6px; font-size: 12px; color: var(--accent); animation: answer-menu-in var(--dur) var(--ease); }
.composer-hint[hidden] { display: none; }
.chat-live-status { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
.msg.notice { transition: opacity 400ms var(--ease); }
.msg.notice.is-leaving { opacity: 0; }
/* 訊息縮圖是按鈕：鍵盤也能放大 */
.msg-thumb { display: block; padding: 0; border: 0; background: none; border-radius: var(--radius-sm); cursor: zoom-in; }
.msg-thumb:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
/* 題目導覽軌在觸控螢幕上加大點擊範圍 */
@media (pointer: coarse) { .question-nav-item { flex-basis: 30px; } }
}

@layer themes { html[lang="en"] { --ui-progress: "Progress"; --ui-start-explanation: "Click a question in the PDF to start"; } }