@font-face {
      font-family: 'ThecircleM';
      src: url('https://cdn.jsdelivr.net/gh/projectnoonnu/noonfonts_two@1.0/ThecircleM.woff') format('woff');
      font-weight: normal;
      font-display: swap;
    }

    /* ==========================================================================
       STUDIUM : ULTRA-MINIMALIST MONOCHROME TYPOGRAPHIC SYSTEM
       ========================================================================== */
    :root {
      --bg: #ffffff;
      --text: #111111;
      --text-muted: #737373;
      --border: #e5e5e5;
      --line-active: #000000;
      --font-brand: 'Shantell Sans', cursive, -apple-system, sans-serif;
      --font-ui: 'ThecircleM', "PingFang SC", "Noto Sans SC", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
      --font-zh: "PingFang SC", "Noto Sans SC", "Songti SC", sans-serif;
      --font-py: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }

    @media (prefers-color-scheme: dark) {
      :root {
        --bg: #000000;
        --text: #f5f5f5;
        --text-muted: #787878;
        --border: #1a1a1a;
        --line-active: #ffffff;
      }
    }

    :root[data-theme="light"] {
      --bg: #ffffff;
      --text: #111111;
      --text-muted: #737373;
      --border: #e5e5e5;
      --line-active: #000000;
    }

    :root[data-theme="dark"] {
      --bg: #000000;
      --text: #f5f5f5;
      --text-muted: #787878;
      --border: #1a1a1a;
      --line-active: #ffffff;
    }

    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      -webkit-tap-highlight-color: transparent;
    }

    body {
      background: var(--bg);
      color: var(--text);
      font-family: var(--font-ui);
      min-height: 100vh;
      padding-bottom: 72px;
      user-select: none;
      -webkit-user-select: none;
      -webkit-font-smoothing: antialiased;
    }

    /* Top Brand Header */
    header {
      position: sticky;
      top: 0;
      z-index: 50;
      background: var(--bg);
      border-bottom: 1px solid var(--border);
      padding: 14px 18px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    .brand-title {
      font-family: var(--font-brand);
      font-size: 1.32rem;
      font-weight: 750;
      letter-spacing: 0.14em;
      text-transform: uppercase;
      color: var(--text);
      display: inline-flex;
      align-items: center;
      justify-content: center;
    }

    /* Screen Views */
    .screen {
      display: none;
      max-width: 680px;
      margin: 0 auto;
      padding: 0 18px;
    }

    .screen.active {
      display: block;
    }

    /* Text Selector Tabs (No boxes, no pills) */
    .sub-nav {
      display: flex;
      gap: 20px;
      border-bottom: 1px solid var(--border);
      overflow-x: auto;
      scrollbar-width: none;
      margin-bottom: 16px;
    }

    .sub-nav::-webkit-scrollbar {
      display: none;
    }

    .sub-nav-item {
      padding: 12px 2px;
      font-size: 0.85rem;
      color: var(--text-muted);
      cursor: pointer;
      white-space: nowrap;
      position: relative;
      transition: color 0.15s;
    }

    .sub-nav-item.active {
      color: var(--text);
      font-weight: 600;
    }

    .sub-nav-item.active::after {
      content: '';
      position: absolute;
      bottom: -1px;
      left: 0;
      right: 0;
      height: 1.5px;
      background: var(--line-active);
    }

    /* Section Numbers (Minimalist horizontal row) */
    .num-selector {
      display: flex;
      gap: 14px;
      overflow-x: auto;
      scrollbar-width: none;
      padding-bottom: 12px;
      border-bottom: 1px solid var(--border);
      margin-bottom: 18px;
    }

    .num-selector::-webkit-scrollbar {
      display: none;
    }

    .num-btn {
      font-size: 0.82rem;
      color: var(--text-muted);
      cursor: pointer;
      white-space: nowrap;
      padding: 2px 0;
    }

    .num-btn.active {
      color: var(--text);
      font-weight: 700;
      border-bottom: 1px solid var(--line-active);
    }

    /* Minimalist Schedule Items */
    .course-row {
      padding: 20px 0;
      border-bottom: 1px solid var(--border);
    }

    .course-title {
      font-size: 1.05rem;
      font-weight: 600;
      margin-bottom: 6px;
      color: var(--text);
    }

    .course-meta {
      font-size: 0.82rem;
      color: var(--text-muted);
      margin-bottom: 12px;
      display: flex;
      gap: 12px;
      flex-wrap: wrap;
    }

    .task-row {
      display: flex;
      align-items: flex-start;
      gap: 10px;
      padding: 8px 0;
      font-size: 0.88rem;
      line-height: 1.45;
      color: var(--text);
    }

    .task-row input[type="checkbox"] {
      margin-top: 3px;
      accent-color: var(--text);
    }

    /* Minimalist Reader Sentences */
    .reader-header {
      display: flex;
      justify-content: space-between;
      align-items: baseline;
      padding: 14px 0 10px;
      font-size: 0.82rem;
      color: var(--text-muted);
    }

    .toggle-action {
      cursor: pointer;
      text-decoration: underline;
      margin-left: 12px;
    }

    .sentence-row {
      padding: 18px 0;
      border-bottom: 1px solid var(--border);
    }

    .sentence-zh-wrap {
      display: flex;
      justify-content: space-between;
      align-items: baseline;
      gap: 12px;
      margin-bottom: 6px;
    }

    .sentence-zh {
      font-family: var(--font-zh);
      font-size: 1.25rem;
      line-height: 1.55;
      color: var(--text);
      letter-spacing: 0.02em;
      flex: 1;
    }

    .zh-w {
      cursor: pointer;
      border-bottom: 1px dotted transparent;
      transition: border-bottom 0.15s, background 0.15s;
      padding: 0 1px;
    }

    .zh-w:hover {
      border-bottom: 1px dotted var(--text);
    }

    .speaker-btn {
      background: transparent;
      border: none;
      color: var(--text-muted);
      cursor: pointer;
      padding: 4px;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      transition: color 0.15s;
      flex-shrink: 0;
    }

    .speaker-btn:hover {
      color: var(--text);
    }

    .sentence-py {
      font-family: var(--font-py);
      font-size: 0.86rem;
      line-height: 1.45;
      color: var(--text-muted);
      font-style: italic;
      margin-bottom: 6px;
    }

    .sentence-kr {
      font-size: 0.9rem;
      line-height: 1.5;
      color: var(--text);
    }

    .hide-py .sentence-py { display: none; }
    .hide-kr .sentence-kr { display: none; }

    /* Word Inspector Drawer (Ultra-Minimalist Monochrome) */
    .inspector-drawer {
      position: fixed;
      bottom: 56px;
      left: 0;
      right: 0;
      background: var(--bg);
      border-top: 1px solid var(--border);
      border-bottom: 1px solid var(--border);
      z-index: 100;
      transform: translateY(150%);
      transition: transform 0.22s cubic-bezier(0.16, 1, 0.3, 1);
    }

    .inspector-drawer.open {
      transform: translateY(0);
    }

    .inspector-inner {
      max-width: 680px;
      margin: 0 auto;
      padding: 16px 20px 20px 20px;
    }

    .inspector-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 6px;
    }

    .inspector-title-row {
      display: inline-flex;
      align-items: center;
      gap: 10px;
    }

    .inspector-zh {
      font-family: var(--font-zh);
      font-size: 1.75rem;
      font-weight: 600;
      color: var(--text);
      letter-spacing: 0.04em;
    }

    .inspector-speaker {
      padding: 4px;
    }

    .inspector-close {
      background: transparent;
      border: none;
      color: var(--text-muted);
      font-size: 1.2rem;
      cursor: pointer;
      padding: 4px 8px;
      line-height: 1;
    }

    .inspector-close:hover {
      color: var(--text);
    }

    .inspector-meta {
      display: flex;
      align-items: center;
      gap: 8px;
      font-size: 0.85rem;
      color: var(--text-muted);
      margin-bottom: 12px;
      flex-wrap: wrap;
    }

    .inspector-py {
      font-family: var(--font-py);
      font-style: italic;
      color: var(--text);
      font-size: 0.95rem;
    }

    .inspector-divider {
      color: var(--border);
    }

    .inspector-level {
      border: 1px solid var(--border);
      padding: 1px 6px;
      font-size: 0.74rem;
      letter-spacing: 0.04em;
      color: var(--text);
    }

    .inspector-body {
      margin-bottom: 14px;
    }

    .inspector-kr {
      font-size: 1.02rem;
      line-height: 1.5;
      color: var(--text);
      font-weight: 500;
      margin-bottom: 4px;
    }

    .inspector-note {
      font-size: 0.82rem;
      line-height: 1.5;
      color: var(--text-muted);
    }

    .inspector-footer {
      display: flex;
      justify-content: flex-end;
    }

    .inspector-save-btn {
      background: transparent;
      border: 1px solid var(--text);
      color: var(--text);
      font-family: var(--font-ui);
      font-size: 0.82rem;
      padding: 6px 14px;
      cursor: pointer;
      transition: background 0.15s, color 0.15s;
    }

    .inspector-save-btn.saved {
      background: var(--text);
      color: var(--bg);
    }

    /* Minimalist Flashcard */
    .flashcard-area {
      min-height: 280px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      text-align: center;
      padding: 40px 20px;
      border-bottom: 1px solid var(--border);
      cursor: pointer;
    }

    .fc-counter {
      font-size: 0.78rem;
      letter-spacing: 0.08em;
      color: var(--text-muted);
      margin-bottom: 18px;
    }

    .fc-word-row {
      display: inline-flex;
      align-items: center;
      gap: 12px;
      margin-bottom: 14px;
    }

    .fc-word {
      font-family: var(--font-zh);
      font-size: 2.8rem;
      font-weight: 500;
      color: var(--text);
      letter-spacing: 0.04em;
    }

    .fc-py {
      font-size: 1.15rem;
      font-style: italic;
      color: var(--text-muted);
      margin-bottom: 10px;
    }

    .fc-kr {
      font-size: 1.25rem;
      color: var(--text);
      margin-bottom: 10px;
    }

    .fc-note {
      font-size: 0.85rem;
      color: var(--text-muted);
      line-height: 1.5;
      max-width: 80%;
    }

    .fc-actions {
      display: flex;
      justify-content: space-between;
      align-items: center;
      padding: 16px 0;
      border-bottom: 1px solid var(--border);
    }

    .fc-btn {
      background: transparent;
      border: none;
      color: var(--text);
      font-size: 0.9rem;
      cursor: pointer;
      padding: 8px 12px;
    }

    .fc-check-btn {
      background: transparent;
      border: 1px solid var(--text);
      color: var(--text);
      padding: 6px 14px;
      font-size: 0.82rem;
      cursor: pointer;
    }

    .fc-check-btn.checked {
      background: var(--text);
      color: var(--bg);
    }

    /* Minimalist Exam Accordion */
    .exam-row {
      padding: 18px 0;
      border-bottom: 1px solid var(--border);
    }

    .exam-q {
      font-size: 0.98rem;
      font-weight: 600;
      line-height: 1.45;
      color: var(--text);
      cursor: pointer;
      display: flex;
      justify-content: space-between;
      align-items: baseline;
      gap: 10px;
    }

    .exam-a {
      display: none;
      padding-top: 12px;
      font-size: 0.88rem;
      line-height: 1.65;
      color: var(--text-muted);
      white-space: pre-line;
    }

    .exam-row.open .exam-a {
      display: block;
      color: var(--text);
    }

    /* Bottom Nav Bar (Minimalist Line & Text) */
    nav.bottom-nav {
      position: fixed;
      bottom: 0;
      left: 0;
      right: 0;
      height: 56px;
      background: var(--bg);
      border-top: 1px solid var(--border);
      display: flex;
      justify-content: space-around;
      align-items: center;
      z-index: 100;
      padding-bottom: env(safe-area-inset-bottom, 0px);
      max-width: 680px;
      margin: 0 auto;
    }

    .nav-btn {
      flex: 1;
      height: 100%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 0.82rem;
      letter-spacing: 0.05em;
      color: var(--text-muted);
      cursor: pointer;
      transition: color 0.15s;
      user-select: none;
    }

    .nav-btn.active {
      color: var(--text);
      font-weight: 700;
    }

    .nav-btn svg {
      display: block;
      stroke: currentColor;
    }

    /* Font Size Customization */
    body.font-large .sentence-zh {
      font-size: 1.45rem;
    }

    /* Minimalist Settings Screen */
    .setting-section {
      padding: 24px 0;
      border-bottom: 1px solid var(--border);
    }

    .setting-title {
      font-size: 0.96rem;
      font-weight: 600;
      color: var(--text);
      margin-bottom: 5px;
      letter-spacing: -0.01em;
    }

    .setting-desc {
      font-size: 0.8rem;
      color: var(--text-muted);
      line-height: 1.55;
      margin-bottom: 14px;
    }

    .setting-options {
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
    }

    button.setting-btn {
      -webkit-appearance: none;
      -moz-appearance: none;
      appearance: none;
      background: transparent !important;
      border: 1px solid var(--border) !important;
      color: var(--text-muted) !important;
      font-size: 0.84rem;
      padding: 8px 16px;
      cursor: pointer;
      border-radius: 0 !important;
      outline: none;
      font-family: inherit;
      transition: border-color 0.15s, color 0.15s;
    }

    button.setting-btn:hover {
      border-color: var(--text-muted) !important;
      color: var(--text) !important;
    }

    button.setting-btn.active {
      border-color: var(--line-active) !important;
      color: var(--text) !important;
      font-weight: 700;
    }