:root {
    --blue: #3b82f6;
    --blue-hover: #2563eb;
    --blue-light: #1e293b;
    --green: #22c55e;
    --green-bg: #14271c;
    --red: #f87171;
    --red-bg: #2a1717;
    --yellow: #fbbf24;
    --explain-bg: #2a2410;
    --explain-border: #5c4a16;
    --gray: #1f2937;
    --border: #374151;
    --bg: #0f172a;
    --card: #1e293b;
    --text: #e5e7eb;
    --muted: #9ca3af;
    --radius: 10px;
  }
  * { box-sizing: border-box; margin: 0; padding: 0; }
  html, body { width: 100%; height: 100%; overflow: hidden; }
  body { font-family: "Noto Sans TC", system-ui, sans-serif; background: var(--bg); color: var(--text); min-height: 100vh; }
  .auth-screen { position: fixed; inset: 0; z-index: 100; display: flex; align-items: center; justify-content: center; padding: 18px; background: var(--bg); overflow: auto; }
  .auth-card { width: min(420px, 100%); border: 1px solid var(--border); border-radius: var(--radius); background: var(--card); padding: 22px; box-shadow: 0 24px 80px rgba(0,0,0,.38); }
  .auth-title { font-size: 1.35rem; font-weight: 800; color: var(--blue); margin-bottom: 6px; }
  .auth-subtitle { color: var(--muted); font-size: .88rem; line-height: 1.6; margin-bottom: 18px; }
  .auth-tabs { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; margin-bottom: 14px; }
  .auth-tab { min-height: 40px; border: 1px solid var(--border); border-radius: var(--radius); background: transparent; color: var(--text); cursor: pointer; font-weight: 700; }
  .auth-tab.active { border-color: var(--blue); background: var(--blue-light); color: #fff; }
  .auth-form { display: grid; gap: 10px; }
  .auth-field { display: grid; gap: 6px; }
  .auth-field label { color: var(--muted); font-size: .82rem; }
  .auth-field input { width: 100%; min-height: 42px; border: 1px solid var(--border); border-radius: var(--radius); background: #0b1222; color: var(--text); padding: 9px 11px; font-size: .95rem; }
  .auth-field input:focus { outline: none; border-color: var(--blue); box-shadow: 0 0 0 3px rgba(59, 130, 246, .18); }
  .password-wrap { position: relative; display: block; }
  .password-wrap input { padding-right: 44px; }
  .password-toggle { position: absolute; top: 50%; right: 6px; transform: translateY(-50%); width: 34px; height: 34px; border: 1px solid transparent; border-radius: 8px; background: transparent; color: var(--muted); cursor: pointer; line-height: 1; display: grid; place-items: center; }
  .password-toggle:hover, .password-toggle:focus-visible { border-color: var(--blue); color: var(--blue); outline: none; }
  .password-toggle::before { content: ""; width: 19px; height: 12px; border: 2px solid currentColor; border-radius: 999px / 680px; display: block; }
  .password-toggle::after { content: ""; position: absolute; width: 6px; height: 6px; border-radius: 50%; background: currentColor; }
  .password-toggle.visible::before { transform: rotate(-18deg); }
  .password-toggle.visible::after { width: 22px; height: 2px; border-radius: 2px; background: currentColor; transform: rotate(-38deg); }
  .remember-row { display: flex; align-items: center; gap: 8px; color: var(--muted); font-size: .84rem; line-height: 1.4; }
  .remember-row input { width: 16px; height: 16px; accent-color: var(--blue); }
  .auth-submit { min-height: 44px; border: 0; border-radius: var(--radius); background: var(--blue); color: #fff; font-weight: 800; cursor: pointer; }
  .auth-submit:hover:not(:disabled) { background: var(--blue-hover); }
  .auth-submit:disabled { opacity: .55; cursor: wait; }
  .auth-secondary { min-height: 42px; border: 1px solid var(--border); border-radius: var(--radius); background: transparent; color: var(--text); font-weight: 700; cursor: pointer; }
  .auth-secondary:hover:not(:disabled), .auth-secondary:focus-visible { border-color: var(--blue); color: var(--blue); outline: none; }
  .auth-secondary:disabled { opacity: .55; cursor: wait; }
  .auth-error { min-height: 20px; color: var(--red); font-size: .84rem; line-height: 1.5; }
  .app.auth-locked { visibility: hidden; pointer-events: none; }

  /* ?€?€ Layout ?€?€ */
  .app { max-width: 1040px; height: 100svh; margin: 0 auto; padding: 14px 16px 16px; display: flex; flex-direction: column; min-height: 0; }
  header { text-align: center; margin-bottom: 10px; flex: 0 0 auto; }
  header h1 { font-size: 1.45rem; color: var(--blue); margin-bottom: 2px; }
  header p { color: var(--muted); font-size: 0.82rem; }
  .sync-strip { display: flex; align-items: center; justify-content: space-between; gap: 12px; border: 1px solid var(--border); border-radius: var(--radius); padding: 8px 10px; margin: 0 0 8px; background: rgba(30, 41, 59, .72); flex: 0 0 auto; }
  .sync-main { display: flex; align-items: center; gap: 8px; min-width: 0; color: var(--muted); font-size: .84rem; }
  .sync-dot { width: 9px; height: 9px; border-radius: 50%; flex: 0 0 9px; background: var(--muted); }
  .sync-strip.online .sync-dot { background: var(--green); }
  .sync-strip.offline .sync-dot { background: var(--red); }
  .sync-strip.pending .sync-dot { background: var(--yellow); }
  .sync-text { overflow-wrap: anywhere; }
  .sync-action { flex: 0 0 auto; padding: 6px 10px; border: 1px solid var(--border); border-radius: var(--radius); background: transparent; color: var(--text); cursor: pointer; font-size: .82rem; }
  .sync-action:hover:not(:disabled) { border-color: var(--blue); color: var(--blue); }
  .sync-action:disabled { opacity: .45; cursor: not-allowed; }
  .sync-actions { display: flex; align-items: center; gap: 8px; flex: 0 0 auto; }
  .user-pill { border: 1px solid transparent; border-radius: var(--radius); background: transparent; color: var(--muted); font-size: .8rem; max-width: 150px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; cursor: pointer; padding: 6px 8px; }
  .user-pill:hover { border-color: var(--blue); color: var(--blue); background: rgba(59, 130, 246, .08); }
  .account-modal { position: fixed; inset: 0; z-index: 60; display: none; align-items: center; justify-content: center; padding: 18px; background: rgba(2, 6, 23, .72); }
  .account-modal.open { display: flex; }
  .account-dialog { width: min(460px, 94vw); max-height: min(620px, 86svh); display: flex; flex-direction: column; border: 1px solid var(--border); border-radius: var(--radius); background: var(--card); box-shadow: 0 24px 80px rgba(0,0,0,.42); overflow: hidden; }
  .account-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 12px 14px; border-bottom: 1px solid var(--border); }
  .account-head .title { font-weight: 800; }
  .account-close { width: 34px; height: 34px; border: 1px solid var(--border); border-radius: var(--radius); background: transparent; color: var(--text); cursor: pointer; font-size: 1.1rem; line-height: 1; }
  .account-close:hover { border-color: var(--blue); color: var(--blue); }
  .account-body { overflow: auto; padding: 14px; display: grid; gap: 14px; }
  .account-kv { display: grid; grid-template-columns: 92px minmax(0, 1fr); gap: 8px 12px; font-size: .86rem; }
  .account-kv .key { color: var(--muted); }
  .account-kv .value { overflow-wrap: anywhere; }
  .account-section { border-top: 1px solid var(--border); padding-top: 12px; }
  .account-section-title { font-weight: 800; margin-bottom: 10px; }
  .account-form { display: grid; gap: 10px; }
  .account-field { display: grid; gap: 6px; }
  .account-field label { color: var(--muted); font-size: .82rem; }
  .account-field input { width: 100%; min-height: 40px; border: 1px solid var(--border); border-radius: var(--radius); background: #0b1222; color: var(--text); padding: 9px 11px; font-size: .92rem; }
  .account-field input:focus { outline: none; border-color: var(--blue); box-shadow: 0 0 0 3px rgba(59, 130, 246, .18); }
  .account-submit { min-height: 42px; border: 1px solid var(--blue); border-radius: var(--radius); background: var(--blue); color: #fff; font-weight: 800; cursor: pointer; }
  .account-submit:disabled { opacity: .55; cursor: wait; }
  .account-message { min-height: 20px; color: var(--muted); font-size: .84rem; line-height: 1.5; }
  .account-message.error { color: var(--red); }
  .account-message.ok { color: var(--green); }
  .sync-panel { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 8px; border: 1px solid var(--border); border-radius: var(--radius); padding: 8px 10px; margin: 0 0 10px; background: rgba(15, 23, 42, .72); flex: 0 0 auto; }
  .sync-stat { min-width: 0; }
  .sync-stat.clickable { width: 100%; text-align: left; border: 1px solid transparent; border-radius: 8px; background: transparent; color: inherit; padding: 6px 8px; cursor: pointer; }
  .sync-stat.clickable:hover { border-color: var(--blue); background: rgba(59, 130, 246, .08); }
  .sync-stat.clickable.active { border-color: var(--blue); background: var(--blue-light); }
  .sync-stat .label { display: flex; align-items: center; gap: 5px; color: var(--muted); font-size: .72rem; margin-bottom: 2px; }
  .sync-stat .icon { display: inline-grid; place-items: center; min-width: 1.35em; min-height: 1.35em; font-family: "Segoe UI Emoji", "Apple Color Emoji", "Noto Color Emoji", system-ui, sans-serif; font-size: .95rem; line-height: 1.2; overflow: visible; filter: drop-shadow(0 1px 0 rgba(0,0,0,.25)); }
  .sync-stat .value { font-size: .9rem; font-weight: 600; overflow-wrap: anywhere; }
  .sync-stat[data-sync-detail="favorites"] .value { color: var(--yellow); }
  .sync-stat[data-sync-detail="wrong"] .value { color: var(--red); }
  .sync-stat.wide { grid-column: span 1; }
  .sync-scope { grid-column: 1 / -1; color: var(--muted); font-size: .78rem; padding: 0 8px 2px; overflow-wrap: anywhere; }
  .sync-detail-modal { position: fixed; inset: 0; z-index: 50; display: none; align-items: center; justify-content: center; padding: 18px; background: rgba(2, 6, 23, .72); }
  .sync-detail-modal.open { display: flex; }
  .sync-detail-dialog { width: min(920px, 94vw); height: min(680px, 86svh); display: flex; flex-direction: column; border: 1px solid var(--border); border-radius: var(--radius); background: var(--card); box-shadow: 0 24px 80px rgba(0,0,0,.42); overflow: hidden; }
  .sync-detail-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 12px 14px; border-bottom: 1px solid var(--border); }
  .sync-detail-head .title { font-weight: 700; }
  .sync-detail-close { width: 34px; height: 34px; border: 1px solid var(--border); border-radius: var(--radius); background: transparent; color: var(--text); cursor: pointer; font-size: 1.1rem; line-height: 1; }
  .sync-detail-close:hover { border-color: var(--blue); color: var(--blue); }
  .sync-detail { min-height: 0; flex: 1 1 auto; font-size: .84rem; line-height: 1.55; overflow: hidden; }
  .sync-detail-layout { height: 100%; display: grid; grid-template-columns: minmax(220px, .86fr) minmax(0, 1.4fr); min-height: 0; }
  .sync-detail-list { border-right: 1px solid var(--border); overflow: auto; padding: 10px; display: grid; align-content: start; gap: 8px; min-height: 0; }
  .sync-detail-row { width: 100%; border: 1px solid var(--border); border-radius: 8px; background: rgba(15, 23, 42, .44); color: var(--text); padding: 10px; text-align: left; cursor: pointer; }
  .sync-detail-row:hover { border-color: var(--blue); background: rgba(59, 130, 246, .08); }
  .sync-detail-row.active { border-color: var(--blue); background: var(--blue-light); }
  .sync-detail-row-title { font-weight: 700; overflow-wrap: anywhere; }
  .sync-detail-row-meta { color: var(--muted); font-size: .78rem; margin-top: 4px; overflow-wrap: anywhere; }
  .sync-detail-pane { overflow: auto; padding: 14px; min-height: 0; }
  .sync-detail-title { font-weight: 700; font-size: 1rem; margin-bottom: 10px; overflow-wrap: anywhere; }
  .sync-detail-section { border-top: 1px solid var(--border); padding-top: 10px; margin-top: 10px; }
  .sync-detail-kv { display: grid; grid-template-columns: minmax(88px, auto) minmax(0, 1fr); gap: 6px 12px; margin-top: 8px; }
  .sync-detail-kv .key { color: var(--muted); }
  .sync-detail-kv .value { overflow-wrap: anywhere; white-space: pre-wrap; }
  .sync-detail-options { display: grid; gap: 6px; margin-top: 8px; }
  .sync-detail-option { border: 1px solid var(--border); border-radius: 8px; padding: 8px 10px; overflow-wrap: anywhere; }
  .sync-detail-option.correct { border-color: var(--green); background: var(--green-bg); }
  .sync-detail-pre { margin-top: 8px; white-space: pre-wrap; overflow-wrap: anywhere; font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: .78rem; color: var(--text); }
  .sync-detail-item { color: var(--text); overflow-wrap: anywhere; }
  .sync-detail-meta { color: var(--muted); font-size: .78rem; }
  .sync-detail-empty { color: var(--muted); }
  .sync-ai-query { margin-top: 8px; }
  .sync-file { display: none; }
  .update-banner { display: flex; align-items: center; justify-content: space-between; gap: 10px; border: 1px solid var(--yellow); border-radius: var(--radius); padding: 10px 12px; margin: -12px 0 20px; background: var(--explain-bg); color: var(--yellow); font-size: .86rem; }
  .update-banner button { flex: 0 0 auto; padding: 6px 10px; border: 1px solid var(--yellow); border-radius: var(--radius); background: transparent; color: var(--yellow); cursor: pointer; }
  .update-banner button:hover { background: rgba(251, 191, 36, .08); }
  .install-banner { display: flex; align-items: center; justify-content: space-between; gap: 10px; border: 1px solid var(--blue); border-radius: var(--radius); padding: 10px 12px; margin: -12px 0 20px; background: var(--blue-light); color: var(--text); font-size: .86rem; }
  .install-banner button { flex: 0 0 auto; padding: 6px 10px; border: 1px solid var(--blue); border-radius: var(--radius); background: var(--blue); color: #fff; cursor: pointer; }
  .install-banner button:hover { background: var(--blue-hover); }
  .legacy-banner { display: flex; align-items: center; justify-content: space-between; gap: 10px; border: 1px solid var(--green); border-radius: var(--radius); padding: 8px 10px; margin: 0 0 8px; background: rgba(20, 39, 28, .82); color: var(--text); font-size: .82rem; flex: 0 0 auto; }
  .legacy-banner strong { color: var(--green); }
  .legacy-actions { display: flex; align-items: center; gap: 8px; flex: 0 0 auto; }
  .legacy-action { padding: 6px 10px; border: 1px solid var(--green); border-radius: var(--radius); background: transparent; color: var(--green); cursor: pointer; font-size: .82rem; }
  .legacy-action.secondary { border-color: var(--border); color: var(--muted); }
  .legacy-action:hover:not(:disabled) { background: rgba(34, 197, 94, .08); }
  .legacy-action:disabled { opacity: .55; cursor: wait; }

  /* ?€?€ Card ?€?€ */
  .card { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px; margin-bottom: 0; min-height: 0; }
  .card-title { font-size: .82rem; font-weight: 600; color: var(--muted); text-transform: uppercase; letter-spacing: .05em; margin-bottom: 10px; }

  /* ?€?€ Setup Panel ?€?€ */
  #setup { display: grid; grid-template-columns: minmax(260px, 1.15fr) minmax(260px, .85fr); grid-template-rows: minmax(0, 1fr) auto auto auto; gap: 12px; flex: 1 1 auto; min-height: 0; overflow: hidden; }
  #setup > .desktop-topic-card { grid-row: span 4; overflow: hidden; display: flex; flex-direction: column; }
  #topics-container { min-height: 0; overflow: auto; padding-right: 2px; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; align-content: start; }
  #topics-container > .loader,
  #topics-container > .no-data { grid-column: 1 / -1; }
  .topics-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; }
  .topic-card { min-width: 0; border: 2px solid var(--border); border-radius: var(--radius); padding: 12px; cursor: pointer; transition: all .15s; }
  .topic-card:hover { border-color: var(--blue); background: var(--blue-light); }
  .topic-card.selected { border-color: var(--blue); background: var(--blue-light); }
  .topic-head { display: grid; grid-template-columns: minmax(0, 1fr) auto; align-items: center; column-gap: 10px; margin-bottom: 4px; min-width: 0; }
  .topic-card .name { min-width: 0; font-weight: 600; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; align-self: center; }
  .topic-card .count { font-size: .82rem; color: var(--muted); }
  .topic-badges { justify-self: end; display: inline-flex; align-items: center; gap: 7px; color: var(--muted); font-size: .74rem; font-weight: 700; line-height: 1; font-variant-numeric: tabular-nums; }
  .topic-badge { display: inline-grid; grid-template-columns: 14px auto; align-items: center; column-gap: 2px; min-height: 16px; white-space: nowrap; }
  .topic-badge .mark { width: 14px; text-align: center; line-height: 1; font-size: .82rem; font-family: "Segoe UI Emoji", "Apple Color Emoji", "Noto Color Emoji", system-ui, sans-serif; filter: drop-shadow(0 1px 0 rgba(0,0,0,.25)); }
  .topic-badge .num { line-height: 16px; }
  .topic-badge.favorite { color: var(--yellow); }
  .topic-badge.wrong { color: var(--red); }
  .topic-progress { display: grid; grid-template-columns: minmax(0, 1fr) auto; align-items: center; gap: 7px; margin-top: 8px; }
  .topic-progress-track { position: relative; height: 4px; border-radius: 999px; background: var(--border); overflow: hidden; }
  .topic-progress-fill { position: absolute; inset: 0; width: var(--pct, 0%); border-radius: inherit; background: var(--blue); transition: width .25s; }
  .topic-progress-wrong { position: absolute; inset: 0; width: var(--wpct, 0%); border-radius: inherit; background: var(--yellow); transition: width .25s; }
  .topic-progress-info { position: relative; display: inline-flex; align-items: center; justify-content: center; width: 16px; height: 16px; border: 1px solid var(--yellow); border-radius: 50%; color: var(--yellow); font-size: .7rem; font-weight: 800; line-height: 1; cursor: help; }

  .review-card { display: flex; align-items: center; gap: 12px; border-left: 4px solid var(--yellow); }
  .review-main { flex: 1; cursor: pointer; }
  .review-card.disabled { border-left-color: var(--border); }
  .review-card.disabled .review-main { cursor: default; }
  .review-card.disabled .review-title { color: var(--muted); }
  .review-title { font-weight: 600; font-size: 1.05rem; margin-bottom: 4px; }
  .review-stat { font-size: .85rem; color: var(--muted); }
  .review-info { position: relative; display: inline-flex; align-items: center; justify-content: center; width: 18px; height: 18px; margin-left: 6px; border: 1px solid var(--yellow); border-radius: 50%; color: var(--yellow); font-size: .78rem; font-weight: 800; vertical-align: 1px; cursor: help; }

  .mode-grid { display: grid; grid-template-columns: 1fr; gap: 8px; }
  .mode-card { border: 2px solid var(--border); border-radius: var(--radius); padding: 10px 12px; cursor: pointer; transition: all .15s; }
  .mode-card:hover { border-color: var(--blue); }
  .mode-card.selected { border-color: var(--blue); background: var(--blue-light); }
  .mode-card.disabled { opacity: .55; cursor: default; }
  .mode-card.disabled:hover { border-color: var(--border); }
  .mode-card .mode-name { font-weight: 600; margin-bottom: 4px; }
  .mode-title-row { display: flex; align-items: center; justify-content: space-between; gap: 10px; }
  .smart-selection-control { display: inline-flex; align-items: center; gap: 7px; flex: 0 0 auto; border: 0; background: transparent; color: var(--text); cursor: pointer; padding: 0; font: inherit; letter-spacing: 0; text-transform: none; }
  .smart-switch-track { position: relative; width: 42px; height: 24px; border-radius: 999px; background: #111827; border: 1px solid var(--border); transition: background .16s, border-color .16s; }
  .smart-switch-knob { position: absolute; top: 3px; left: 3px; width: 16px; height: 16px; border-radius: 50%; background: var(--muted); transition: transform .16s, background .16s; box-shadow: 0 1px 3px rgba(0,0,0,.35); }
  .smart-switch-state { min-width: 26px; color: var(--muted); font-size: .72rem; font-weight: 800; line-height: 1; }
  .smart-switch-label { color: var(--text); font-size: .82rem; font-weight: 800; white-space: nowrap; }
  .smart-selection-control.selected .smart-switch-track { background: var(--blue); border-color: var(--blue); }
  .smart-selection-control.selected .smart-switch-knob { transform: translateX(18px); background: #fff; }
  .smart-selection-control.selected .smart-switch-state { color: var(--blue); }
  .smart-selection-control.disabled { cursor: not-allowed; opacity: .55; }
  .mode-icon { display: inline-block; width: 1.35em; margin-right: 4px; text-align: center; line-height: 1; }
  .mode-card .mode-desc { font-size: .8rem; color: var(--muted); line-height: 1.5; }
  @media (max-width: 520px) { .mode-grid { grid-template-columns: 1fr; } }
  /* Pool breakdown badge */
  .pool-breakdown { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 6px; }
  .pool-tag { display: inline-flex; align-items: center; gap: 4px; padding: 3px 10px; border-radius: 20px; font-size: .78rem; font-weight: 600; border: 1px solid; }
  .pool-tag.fav  { border-color: #fbbf24; color: #fbbf24; background: rgba(251,191,36,.1); }
  .pool-tag.unseen { border-color: #60a5fa; color: #60a5fa; background: rgba(96,165,250,.1); }
  .pool-tag.practice { border-color: #f87171; color: #f87171; background: rgba(248,113,113,.1); }
  .pool-tag.fill { border-color: #9ca3af; color: #9ca3af; background: rgba(156,163,175,.1); }

  .subtopics-panel { margin-top: 16px; }
  .subtopic-trigger-btn { width: 100%; display: flex; align-items: center; justify-content: space-between; padding: 10px 14px; border: 1px solid var(--border); border-radius: 10px; background: var(--card-bg); cursor: pointer; font-size: .9rem; color: var(--text); }
  .subtopic-trigger-btn:hover { border-color: var(--blue); }
  .subtopic-trigger-badge { font-size: .78rem; padding: 2px 8px; border-radius: 10px; background: var(--blue); color: #fff; }
  .subtopic-trigger-badge.all { background: var(--muted); }
  #subtopic-trigger-wrap { }
  #subtopics-container { display: flex; flex-wrap: wrap; gap: 8px; padding: 4px 0; align-content: flex-start; }
  .cat-btn { display: flex; align-items: center; gap: 6px; padding: 8px 14px; border: 1px solid var(--border); border-radius: 10px; background: transparent; color: var(--text); cursor: pointer; font-size: .88rem; transition: all .15s; user-select: none; text-align: left; }
  .cat-btn:hover { border-color: var(--blue); color: var(--blue); }
  .cat-btn.active { background: var(--blue); color: #fff; border-color: var(--blue); }
  .cat-btn.partial { border-color: var(--blue); color: var(--blue); background: var(--blue-light); }
  .cat-btn.all-cat { font-weight: 600; }
  .cat-count { font-size: .75rem; opacity: .7; font-variant-numeric: tabular-nums; }

  .count-row { display: flex; align-items: center; gap: 12px; margin-top: 0; }
  .count-row label { font-size: .9rem; color: var(--text); white-space: nowrap; }
  .count-row input[type=range] { flex: 1; accent-color: var(--blue); }
  .count-badge { background: var(--blue); color: #fff; border-radius: 20px; padding: 2px 12px; font-weight: 700; font-size: .9rem; min-width: 40px; text-align: center; }
  .timer-select { background: var(--gray); color: var(--text); border: 1px solid var(--border); border-radius: var(--radius); padding: 4px 8px; font-size: .88rem; cursor: pointer; }
  /* Exam countdown timer in quiz header */
  .exam-timer { font-size: .85rem; font-weight: 700; font-variant-numeric: tabular-nums; color: var(--blue); background: rgba(59,130,246,.12); border-radius: 20px; padding: 2px 10px; letter-spacing: .02em; }
  .exam-timer.warning { color: var(--red); background: var(--red-bg); animation: timer-pulse 1s ease-in-out infinite; }
  @keyframes timer-pulse { 0%,100% { opacity: 1; } 50% { opacity: .6; } }

  .start-btn { display: block; width: 100%; padding: 12px; background: var(--blue); color: #fff; border: none; border-radius: var(--radius); font-size: 1rem; font-weight: 600; cursor: pointer; transition: background .15s; margin-top: 0; align-self: end; }
  .start-btn:hover:not(:disabled) { background: var(--blue-hover); }
  .start-btn:disabled { background: #475569; color: #94a3b8; cursor: not-allowed; }

  /* ?€?€ Quiz Panel ?€?€ */
  #quiz { display: none; flex: 1 1 auto; flex-direction: column; min-height: 0; overflow: hidden; }
  #quiz .card { height: calc(100% - 58px); overflow: auto; }
  .progress-bar { position: relative; height: 6px; background: var(--border); border-radius: 3px; margin-bottom: 20px; overflow: hidden; }
  .progress-fill { position: absolute; inset: 0; background: var(--blue); border-radius: 3px; transition: width .3s; }
  .progress-wrong { position: absolute; inset: 0; width: 0%; background: var(--red); border-radius: 3px; transition: width .3s; }
  .progress-label { display: flex; justify-content: space-between; font-size: .82rem; color: var(--muted); margin-bottom: 6px; }

  .question-header { display: flex; align-items: center; gap: 10px; margin-bottom: 14px; }
  .q-num { background: var(--blue); color: #fff; border-radius: 6px; padding: 2px 10px; font-size: .85rem; font-weight: 700; }
  .subtopic-tag { background: var(--gray); color: var(--muted); border-radius: 20px; padding: 2px 10px; font-size: .78rem; }
  .favorite-btn { margin-left: auto; width: 34px; height: 34px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--card); color: var(--muted); cursor: pointer; font-size: 1.15rem; line-height: 1; transition: all .15s; }
  .favorite-btn:hover { border-color: var(--yellow); color: var(--yellow); background: var(--explain-bg); }
  .favorite-btn.active { border-color: var(--yellow); color: var(--yellow); background: var(--explain-bg); }
  .favorite-nav-btn { display: none; }
  .question-text { font-size: 1.05rem; line-height: 1.7; margin-bottom: 18px; }

  .options { display: flex; flex-direction: column; gap: 10px; }
  .option-btn { display: flex; align-items: flex-start; gap: 10px; padding: 12px 16px; border: 2px solid var(--border); border-radius: var(--radius); cursor: pointer; transition: all .15s; background: var(--card); color: var(--text); text-align: left; font-size: .95rem; line-height: 1.5; }
  .option-btn:hover:not(:disabled) { border-color: var(--blue); background: var(--blue-light); }
  .option-btn .letter { font-weight: 700; min-width: 20px; color: var(--blue); }
  .option-btn.selected { border-color: var(--blue); background: var(--blue-light); }
  .option-btn.correct { border-color: var(--green); background: var(--green-bg); }
  .option-btn.wrong { border-color: var(--red); background: var(--red-bg); }
  .option-btn:disabled { cursor: default; }

  .nav-row { display: flex; justify-content: space-between; align-items: center; margin-top: 10px; gap: 10px; flex: 0 0 auto; }
  .nav-btn { padding: 10px 20px; border: 1px solid var(--border); border-radius: var(--radius); cursor: pointer; font-size: .9rem; background: var(--card); color: var(--text); transition: all .15s; }
  .nav-btn:hover:not(:disabled) { border-color: var(--blue); color: var(--blue); }
  .nav-btn:disabled { opacity: .4; cursor: not-allowed; }
  .nav-btn.primary { background: var(--blue); color: #fff; border-color: var(--blue); }
  .nav-btn.primary:hover:not(:disabled) { background: var(--blue-hover); }
  .nav-btn.danger { border-color: var(--red); color: var(--red); }
  .nav-btn.danger:hover:not(:disabled) { background: var(--red-bg); color: var(--red); }

  /* Feedback */
  .advance-hint { margin-top: 16px; text-align: center; color: var(--muted); font-size: .82rem; user-select: none; animation: hintpulse 1.6s ease-in-out infinite; }
  @keyframes hintpulse { 0%,100% { opacity: .5; } 50% { opacity: 1; } }
  .feedback-banner { margin-top: 16px; padding: 10px 14px; border-radius: var(--radius); font-size: .9rem; font-weight: 600; }
  .feedback-banner.ok { background: var(--green-bg); color: var(--green); border: 1px solid var(--green); }
  .feedback-banner.ng { background: var(--red-bg); color: var(--red); border: 1px solid var(--red); }
  .audit-info { margin-top: 8px; color: var(--muted); font-size: .78rem; line-height: 1.55; font-weight: 500; }
  .feedback-banner .audit-info { color: inherit; opacity: .82; }
  .audit-copy-row { display: flex; align-items: center; flex-wrap: wrap; gap: 8px; }
  .audit-copy-btn { padding: 3px 8px; border: 1px solid currentColor; border-radius: 6px; background: transparent; color: inherit; cursor: pointer; font-size: .74rem; line-height: 1.35; opacity: .82; }
  .audit-copy-btn:hover { opacity: 1; }

  /* ?€?€ AI 閫?? ?€?€ */
  .explain-box { margin-top: 16px; padding: 16px; background: var(--explain-bg); border: 1px solid var(--explain-border); border-radius: var(--radius); font-size: .9rem; line-height: 1.7; white-space: pre-wrap; }
  .explain-warning { display: block; margin-bottom: 10px; padding: 8px 10px; border: 1px solid var(--yellow); border-radius: var(--radius); color: var(--yellow); background: rgba(245, 158, 11, .1); white-space: normal; }
  .explain-verified { display: block; margin-bottom: 8px; color: var(--green); font-size: .78rem; white-space: normal; }
  .explain-btn { margin-top: 12px; padding: 8px 16px; background: transparent; border: 1px solid var(--yellow); color: var(--yellow); border-radius: var(--radius); cursor: pointer; font-size: .85rem; transition: all .15s; }
  .explain-btn:hover { background: var(--explain-bg); }
  .explain-loading { color: var(--muted); font-size: .85rem; margin-top: 8px; }

  /* ?€?€ Results ?€?€ */
  #results { display: none; flex: 1 1 auto; flex-direction: column; min-height: 0; overflow: hidden; }
  #results .card { height: 100%; display: flex; flex-direction: column; overflow: hidden; }
  #results-list { min-height: 0; overflow: auto; padding-right: 2px; flex: 1 1 auto; }

  /* Score banner — horizontal compact */
  .score-summary { display: flex; align-items: center; gap: 14px; padding-bottom: 10px; border-bottom: 1px solid var(--border); }
  .score-circle { width: 56px; height: 56px; border-radius: 50%; display: flex; align-items: center; justify-content: center; position: relative; flex-shrink: 0; }
  .score-circle::before { content: ''; position: absolute; width: 42px; height: 42px; background: var(--card); border-radius: 50%; }
  .score-num { position: relative; font-size: 1rem; font-weight: 700; }
  .score-summary-text { flex: 1; min-width: 0; }
  .score-summary .big { font-size: 1rem; font-weight: 600; }
  .score-summary .sub { color: var(--muted); font-size: .82rem; margin-top: 2px; }

  /* Tab bar */
  .results-tab-bar { display: flex; border-bottom: 1px solid var(--border); margin-top: 10px; margin-bottom: 10px; flex-shrink: 0; }
  .results-tab { flex: 1; padding: 8px 4px; background: transparent; border: none; border-bottom: 2px solid transparent; color: var(--muted); font-size: .82rem; font-weight: 600; cursor: pointer; transition: color .15s, border-color .15s; margin-bottom: -1px; }
  .results-tab:hover { color: var(--text); }
  .results-tab.tab-wrong.active { color: var(--red); border-bottom-color: var(--red); }
  .results-tab.tab-correct.active { color: var(--green); border-bottom-color: var(--green); }
  .results-tab.tab-all.active { color: var(--blue); border-bottom-color: var(--blue); }

  /* Collapsible result items */
  .result-item { border: 1px solid var(--border); border-radius: var(--radius); margin-bottom: 8px; overflow: hidden; }
  .result-item.correct { border-left: 4px solid var(--green); }
  .result-item.wrong { border-left: 4px solid var(--red); }
  .result-item-summary { display: flex; align-items: center; gap: 8px; padding: 10px 12px; cursor: pointer; user-select: none; -webkit-user-select: none; }
  .result-item-summary:hover { background: rgba(255,255,255,.03); }
  .result-preview { flex: 1; font-size: .88rem; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; min-width: 0; }
  .result-chevron { color: var(--muted); font-size: .75rem; flex-shrink: 0; transition: transform .2s; line-height: 1; }
  .result-item.expanded .result-chevron { transform: rotate(180deg); }
  .result-detail { padding: 10px 14px 12px; border-top: 1px solid var(--border); display: none; }
  .result-item.expanded .result-detail { display: block; }
  .result-header { display: flex; align-items: center; gap: 8px; margin-bottom: 8px; flex-wrap: wrap; }
  .wrong-count-tag { background: var(--red-bg); color: var(--red); border: 1px solid var(--red); border-radius: 20px; padding: 1px 7px; font-size: .72rem; font-weight: 600; flex-shrink: 0; }
  .result-icon { font-size: .9rem; flex-shrink: 0; }
  .result-q { font-size: .95rem; line-height: 1.5; margin-bottom: 6px; }
  .result-ans { font-size: .85rem; display: flex; gap: 16px; flex-wrap: wrap; }
  .result-ans .correct-ans { color: var(--green); font-weight: 600; }
  .result-ans .wrong-ans { color: var(--red); }
  .results-section-header { display: none; }
  .results-section-divider { display: none; }
  /* Subtopic filter chips */
  .result-subtopic-bar { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 10px; flex-shrink: 0; }
  .result-subtopic-chip { background: var(--gray); color: var(--muted); border: 1px solid var(--border); border-radius: 20px; padding: 3px 12px; font-size: .78rem; font-weight: 600; cursor: pointer; transition: background .15s, color .15s, border-color .15s; }
  .result-subtopic-chip:hover { color: var(--text); }
  .result-subtopic-chip.active { background: rgba(59,130,246,.15); color: var(--blue); border-color: var(--blue); }
  /* Time badge in collapsed row */
  .result-time-badge { color: var(--muted); font-size: .75rem; flex-shrink: 0; font-variant-numeric: tabular-nums; }
  /* Slowest-3 summary in score banner */
  .result-time-summary { font-size: .76rem; color: var(--muted); margin-top: 4px; }
  /* Fav button in result detail */
  .result-fav-btn { margin-top: 10px; padding: 5px 14px; background: transparent; border: 1px solid var(--border); border-radius: 20px; color: var(--muted); font-size: .82rem; cursor: pointer; transition: border-color .15s, color .15s; }
  .result-fav-btn:hover { border-color: var(--yellow); color: var(--yellow); }
  .result-fav-btn.active { border-color: var(--yellow); color: var(--yellow); background: rgba(251,191,36,.1); }

  .retry-btn { display: block; width: 100%; padding: 12px; background: transparent; border: 2px solid var(--blue); color: var(--blue); border-radius: var(--radius); font-size: 1rem; font-weight: 600; cursor: pointer; margin-top: 12px; transition: all .15s; flex-shrink: 0; }
  .retry-btn:hover { background: var(--blue); color: #fff; }

  /* ?€?€ Misc ?€?€ */
  .mobile-setup-panel { display: none; }
  .mobile-sheet { position: fixed; inset: 0; z-index: 60; display: none; align-items: center; justify-content: center; padding: 14px; background: rgba(2, 6, 23, .72); }
  .mobile-sheet.open { display: flex; }
  .mobile-sheet-dialog { width: min(440px, 100%); max-height: min(620px, calc(100svh - 28px)); display: flex; flex-direction: column; border: 1px solid var(--border); border-radius: var(--radius); background: var(--card); overflow: hidden; box-shadow: 0 24px 80px rgba(0,0,0,.42); }
  .mobile-sheet-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 12px 14px; border-bottom: 1px solid var(--border); }
  .mobile-sheet-title { font-weight: 700; }
  .mobile-sheet-close { width: 34px; height: 34px; border: 1px solid var(--border); border-radius: var(--radius); background: transparent; color: var(--text); cursor: pointer; font-size: 1.1rem; line-height: 1; }
  .mobile-sheet-body { min-height: 0; overflow: auto; padding: 12px; }
  .mobile-summary-row { display: grid; grid-template-columns: minmax(0, 1fr); gap: 10px; align-items: center; padding: 10px 0; border-bottom: 1px solid var(--border); }
  .mobile-summary-row:last-child { border-bottom: 0; }
  .mobile-summary-trigger { width: 100%; border: 1px solid var(--border); border-radius: var(--radius); background: transparent; color: var(--text); padding: 12px; text-align: left; cursor: pointer; }
  .mobile-summary-trigger:active,
  .mobile-summary-trigger:focus-visible { border-color: var(--blue); background: rgba(59, 130, 246, .08); outline: none; }
  .mobile-topic-card { display: block; }
  .mobile-topic-head { display: flex; align-items: center; justify-content: space-between; gap: 8px; min-width: 0; }
  .mobile-topic-title { min-width: 0; font-weight: 800; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
  .mobile-topic-badges { flex: 0 0 auto; display: inline-flex; align-items: center; gap: 8px; color: var(--muted); font-size: .8rem; font-weight: 800; line-height: 1; font-variant-numeric: tabular-nums; }
  #mobile-topic-favorites { color: var(--yellow); }
  #mobile-topic-wrong { color: var(--red); }
  .mobile-topic-count { margin-top: 7px; color: var(--muted); font-size: .86rem; }
  .mobile-summary-head { display: flex; align-items: center; justify-content: space-between; gap: 10px; }
  .mobile-summary-chevron { flex: 0 0 auto; color: var(--muted); font-size: 1.1rem; line-height: 1; }
  .mobile-summary-label { color: var(--muted); font-size: .74rem; margin-bottom: 2px; }
  .mobile-summary-value { font-weight: 700; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
  .hidden { display: none !important; }
  .loader { text-align: center; padding: 32px; color: var(--muted); }
  .error-msg { color: var(--red); font-size: .9rem; padding: 8px 0; }
  .no-data { text-align: center; padding: 40px; color: var(--muted); }
  .no-data p { margin-bottom: 8px; }
  .no-data code { background: var(--gray); padding: 2px 6px; border-radius: 4px; font-size: .85rem; }
  #topics-container, #quiz .card, #results-list, .sync-detail { scrollbar-width: none; }
  #topics-container::-webkit-scrollbar, #quiz .card::-webkit-scrollbar, #results-list::-webkit-scrollbar, .sync-detail::-webkit-scrollbar { display: none; }

  @media (max-height: 760px) and (min-width: 521px) {
    .app { padding-top: 10px; padding-bottom: 10px; }
    header h1 { font-size: 1.25rem; }
    header p { display: none; }
    .sync-strip { padding: 6px 10px; }
    .sync-panel { padding: 6px 10px; }
    .card { padding: 12px; }
    .mode-card .mode-desc { display: block; font-size: .74rem; line-height: 1.35; }
    .score-circle { width: 48px; height: 48px; }
    .score-circle::before { width: 36px; height: 36px; }
    .score-num { font-size: .9rem; }
  }

  @media (min-width: 821px) and (hover: hover) and (pointer: fine) {
    .mobile-setup-panel { display: none !important; }
  }

  @media (hover: none) and (pointer: coarse) {
    #setup { grid-template-columns: 1fr; grid-template-rows: auto auto auto; gap: 8px; }
    .desktop-topic-card,
    .desktop-mode-card { display: none !important; }
    .mobile-setup-panel { display: block !important; }
    .topics-grid { grid-template-columns: 1fr; }
  }

  @media (max-width: 520px) {
    body { min-height: 100svh; }
    .auth-screen { align-items: flex-start; padding: max(14px, env(safe-area-inset-top)) 12px max(14px, env(safe-area-inset-bottom)); }
    .auth-card { width: 100%; padding: 18px; margin: auto 0; }
    .app { padding: 10px 10px calc(10px + env(safe-area-inset-bottom)); }
    header h1 { font-size: 1.18rem; }
    header p { display: none; }
    header { margin-bottom: 8px; }
    .sync-strip { align-items: stretch; margin-top: 0; }
    .sync-main { align-items: flex-start; line-height: 1.45; }
    .sync-actions { flex-wrap: wrap; justify-content: flex-end; }
    .sync-panel { grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 4px; padding: 5px 6px; margin-bottom: 6px; }
    .sync-scope { display: none; }
    .sync-stat.clickable { min-height: 34px; display: grid; grid-template-columns: auto auto; align-items: center; justify-content: center; column-gap: 3px; padding: 4px 3px; text-align: center; border-radius: 7px; }
    .sync-stat.clickable::before { content: attr(data-mobile-icon); display: inline-grid; place-items: center; min-width: 20px; min-height: 20px; font-family: "Segoe UI Emoji", "Apple Color Emoji", "Noto Color Emoji", system-ui, sans-serif; font-size: .95rem; line-height: 1.2; overflow: visible; }
    .sync-stat .label { display: none; }
    .sync-stat .value { font-size: .78rem; line-height: 1; font-weight: 700; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
    .sync-stat.wide { grid-column: span 1; }
    .sync-stat.wide .value { display: none; }
    .sync-detail-modal { padding: 10px; }
    .sync-detail-dialog { width: 100%; height: min(560px, calc(100svh - 20px)); }
    .account-modal { align-items: flex-end; padding: 10px; }
    .account-dialog { width: 100%; max-height: min(620px, calc(100svh - 20px)); }
    .account-kv { grid-template-columns: 82px minmax(0, 1fr); }
    .sync-detail-layout { grid-template-columns: 1fr; grid-template-rows: minmax(120px, .45fr) minmax(0, 1fr); }
    .sync-detail-list { border-right: 0; border-bottom: 1px solid var(--border); }
    .update-banner { align-items: stretch; flex-direction: column; }
    .install-banner { align-items: stretch; flex-direction: column; }
    .legacy-banner { align-items: stretch; flex-direction: column; }
    .legacy-actions { display: grid; grid-template-columns: 1fr 1fr; }
    .card { padding: 12px; margin-bottom: 0; }
    body.quiz-active header,
    body.quiz-active .sync-strip,
    body.quiz-active .sync-panel,
    body.quiz-active .update-banner,
    body.quiz-active .install-banner { display: none !important; }
    body.quiz-active .legacy-banner { display: none !important; }
    body.quiz-active .app { padding-top: 8px; }
    #setup { grid-template-columns: 1fr; grid-template-rows: auto auto auto; gap: 8px; }
    .desktop-topic-card,
    .desktop-mode-card { display: none; }
    .mobile-setup-panel { display: block; }
    .topics-grid { grid-template-columns: 1fr; }
    .mode-grid { grid-template-columns: 1fr; }
    .mode-card .mode-desc { display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; font-size: .74rem; line-height: 1.35; }
    .count-row { align-items: stretch; flex-wrap: wrap; }
    .count-row input[type=range] { flex-basis: 100%; order: 3; }
    body.quiz-active #quiz { position: relative; }
    body.quiz-active #quiz .card { height: 100%; padding-bottom: calc(84px + env(safe-area-inset-bottom)); }
    body.quiz-active .progress-label { display: grid; grid-template-columns: 1fr auto; align-items: center; gap: 8px; font-size: .78rem; margin-bottom: 4px; }
    body.quiz-active .progress-bar { height: 3px; margin-bottom: 12px; }
    .question-header { align-items: center; flex-wrap: nowrap; gap: 8px; margin-bottom: 10px; }
    .q-num { padding: 2px 8px; font-size: .78rem; }
    .subtopic-tag { max-width: calc(100% - 92px); overflow-wrap: anywhere; }
    .question-header .favorite-btn { display: none; }
    .question-text { font-size: 1rem; line-height: 1.62; margin-bottom: 14px; }
    .options { gap: 9px; }
    .option-btn { min-height: 52px; padding: 13px 12px; align-items: flex-start; font-size: .95rem; line-height: 1.45; }
    .option-btn .letter { min-width: 22px; }
    .feedback-banner { margin-top: 12px; padding: 9px 11px; font-size: .85rem; line-height: 1.45; }
    .explain-btn { width: 100%; min-height: 42px; }
    .explain-box { max-height: min(260px, 38svh); overflow: auto; padding: 12px; font-size: .85rem; line-height: 1.6; }
    .advance-hint { margin-top: 10px; font-size: .78rem; }
    .nav-row { position: fixed; left: 10px; right: 10px; bottom: calc(8px + env(safe-area-inset-bottom)); z-index: 30; display: grid; grid-template-columns: .9fr 1fr .8fr 1fr; align-items: stretch; gap: 8px; margin: 0; padding: 8px; border: 1px solid var(--border); border-radius: var(--radius); background: rgba(15, 23, 42, .96); box-shadow: 0 14px 40px rgba(0,0,0,.42); backdrop-filter: blur(10px); }
    .nav-btn { width: 100%; min-height: 46px; padding: 8px 6px; font-size: .84rem; font-weight: 700; }
    .nav-btn.primary { grid-column: auto; }
    .favorite-nav-btn { display: inline-flex; align-items: center; justify-content: center; min-height: 46px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--card); color: var(--muted); cursor: pointer; font-size: 1.15rem; line-height: 1; }
    .favorite-nav-btn.active { border-color: var(--yellow); color: var(--yellow); background: var(--explain-bg); }
    .result-ans { display: block; }
    .result-ans span { display: block; margin-bottom: 6px; }
  }

  @media (hover: hover) and (pointer: fine) {
    #setup { grid-template-columns: minmax(260px, 1.15fr) minmax(260px, .85fr); grid-template-rows: minmax(0, 1fr) auto auto auto; }
    #setup > .desktop-topic-card { display: flex !important; grid-row: span 4; }
    #setup > .desktop-mode-card { display: block !important; }
    .mobile-setup-panel { display: none !important; }
    #topics-container { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .desktop-topic-card .topics-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  }

  @media (hover: none) and (pointer: coarse) {
    #setup { grid-template-columns: 1fr; grid-template-rows: auto auto auto; gap: 8px; }
    .desktop-topic-card,
    .desktop-mode-card { display: none !important; }
    .mobile-setup-panel { display: block !important; }
    .topics-grid { grid-template-columns: 1fr; }
  }