:root {
      color-scheme: light;
      --bg-color: #f0f2f5;
      --page-bg: #ffffff;
      --text-color: #333333;
      --primary-color: #007acc;
      --surface-color: #f8f9fa;
      --border-color: #e1e4e8;
      --muted-text: #666666;
      --notice-bg: #edf6fd;
      --shadow: 0 8px 24px rgba(0,0,0,.07);
      --text-scale: 1;
    }

    /* Course additions: retain the reference page's colors and type scale. */
    .page-shell { direction: rtl; text-align: right; min-width: 0; overflow-wrap: anywhere; }
    .lesson-list { list-style: none; padding: 0; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); grid-auto-rows: 1fr; gap: 12px; }
    .lesson-list li { display: flex; margin: 0; padding: 0; min-width: 0; }
    .lesson-list a { display: flex; align-items: flex-start; gap: 14px; width: 100%; min-height: 6.3em; padding: 18px 20px; border: 1px solid var(--border-color); border-radius: 10px; background: var(--surface-color); color: var(--text-color); text-decoration: none; }
    .lesson-list a:hover { border-color: var(--primary-color); color: var(--primary-color); }
    .lesson-number { color: var(--primary-color); font-weight: 700; font-size: .85em; line-height: 1.65; flex: 0 0 42px; padding-block-start: .12em; }
    .lesson-label { display: block; flex: 1; min-width: 0; }
    .lesson-title { display: block; line-height: 1.55; }
    .lesson-english { display: block; margin-block-start: 7px; color: var(--muted-text); font-size: .8em; line-height: 1.5; direction: ltr; unicode-bidi: isolate; text-align: right; }
    .lesson-navigation { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 16px; padding: 24px 0; border-top: 1px solid var(--border-color); }
    .download-list { overflow-wrap: anywhere; }
    .code-example { min-width: 0; margin: 26px 0; }
    .code-header { display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap; }
    .code-header h3 { font-size: .9em; margin: 0; min-width: 0; overflow-wrap: anywhere; }
    .copy-code { font-size: .8em; border-radius: 8px; }
    .copy-status { display: block; color: var(--primary-color); font-size: .8em; }
    .code-block { overflow-wrap: normal; white-space: pre; }
    .code-block code { direction: ltr; unicode-bidi: isolate; text-align: left; }
    @media (max-width: 900px) { .lesson-list { grid-template-columns: 1fr; grid-auto-rows: auto; } .lesson-list a { padding: 16px; gap: 10px; } }
    @media (max-width: 380px) { .page-shell { padding-inline: 14px; } .zoom-actions { gap: 4px; flex-wrap: wrap; } .reading-tools { gap: 3px; padding-inline: 6px; } .reading-tools .control { padding-inline: 8px; } }
    @media print { .copy-code, .copy-status, .lesson-navigation { display: none; } }
    :root[data-theme="dark"] {
      color-scheme: dark;
      --bg-color: #0f172a;
      --page-bg: #111827;
      --text-color: #e5e7eb;
      --primary-color: #55b9ff;
      --surface-color: #1f2937;
      --border-color: #374151;
      --muted-text: #cbd5e1;
      --notice-bg: #142c43;
      --shadow: 0 8px 24px rgba(0,0,0,.18);
    }
    * { box-sizing: border-box; }
    html { scroll-behavior: smooth; scroll-padding-top: 24px; }
    body {
      margin: 0; padding: 24px 0 110px;
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      background: var(--bg-color); color: var(--text-color);
      transition: background-color .2s, color .2s;
    }
    .page-shell {
      width: min(1180px, calc(100% - 32px)); margin-inline: auto; padding: 42px 48px 32px;
      font-size: calc(18px * var(--text-scale)); line-height: 1.85;
      background: var(--page-bg); border: 1px solid var(--border-color);
      border-top: 5px solid var(--primary-color); border-radius: 16px; box-shadow: var(--shadow);
    }
    .panel {
      margin: 0 0 46px; padding: 0;
    }
    .cover { margin-bottom: 30px; padding-bottom: 30px; border-bottom: 1px solid var(--border-color); }
    #contents { padding-bottom: 30px; border-bottom: 1px solid var(--border-color); }
    .eyebrow { color: var(--muted-text); font-size: .85em; margin: 0 0 12px; }
    h1 { margin: 0 0 14px; font-size: 2.15em; line-height: 1.5; color: var(--primary-color); }
    .cover .subtitle { font-size: 1.1em; margin: 0; }
    .cover .meta { margin: 18px 0 0; color: var(--muted-text); font-size: .85em; }
    h2 { margin: 0 0 20px; font-size: 1.65em; line-height: 1.5; color: var(--primary-color); }
    h3 { font-size: 1.15em; margin: 0 0 8px; }
    p { margin: 0 0 14px; }
    p:last-child { margin-bottom: 0; }
    ul, ol { margin: 8px 0 16px; padding-inline-start: 1.6em; }
    li { margin-block: 5px; padding-inline-start: .2em; }
    a { color: var(--primary-color); text-underline-offset: 4px; }
    bdi, .unit { unicode-bidi: isolate; direction: ltr; }
    .unit { direction: ltr; display: inline-block; }
    .toc-intro { color: var(--muted-text); font-size: .9em; }
    .toc-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 6px 24px; list-style: none; margin: 0; padding: 0; counter-reset: section; }
    .toc-list li { margin: 0; padding: 0; }
    .toc-list a { display: flex; align-items: baseline; gap: 10px; padding: 8px 10px; border-radius: 8px; color: var(--text-color); text-decoration: none; line-height: 1.6; }
    .toc-list a::before { counter-increment: section; content: counter(section, decimal-leading-zero); color: var(--primary-color); font-weight: 700; font-size: .85em; }
    .toc-list a:hover { background: var(--surface-color); color: var(--primary-color); }
    :focus-visible { outline: 3px solid var(--primary-color); outline-offset: 4px; }
    .back-link { display: inline-block; margin-top: 18px; font-size: .8em; text-decoration: none; }
    .back-link:hover { text-decoration: underline; }
    .notice { margin-block: 22px; padding: 18px 22px; border-inline-start: 4px solid var(--primary-color); background: var(--notice-bg); border-radius: 8px; }
    .components { columns: 2; column-gap: 40px; }
    .components li { break-inside: avoid; }
    .figure { margin: 26px 0 10px; }
    .image-placeholder {
      min-height: 210px; padding: 30px 24px; display: flex; flex-direction: column;
      justify-content: center; align-items: center; gap: 10px; text-align: center;
      border: 2px dashed var(--border-color); border-radius: 12px; background: var(--surface-color);
    }
    .placeholder-number { font-size: .9em; font-weight: 700; color: var(--primary-color); }
    .placeholder-label { font-size: 1.15em; font-weight: 600; }
    .placeholder-description { max-width: 760px; font-size: .95em; color: var(--muted-text); line-height: 1.8; }
    figcaption { text-align: center; color: var(--muted-text); margin-top: 10px; font-size: .8em; }
    .figure img { display: block; width: auto; height: auto; max-width: 100%; max-height: 540px; margin-inline: auto; border-radius: 10px; cursor: zoom-in; }
    .flow { direction: ltr; unicode-bidi: isolate; text-align: center; padding: 18px; margin: 18px 0; border: 1px solid var(--border-color); border-radius: 10px; background: var(--surface-color); font-weight: 600; line-height: 2; }
    .table-wrap { overflow-x: auto; margin: 22px 0; border: 1px solid var(--border-color); border-radius: 10px; }
    table { width: 100%; border-collapse: collapse; text-align: right; }
    th, td { padding: 14px 20px; border-bottom: 1px solid var(--border-color); }
    th { color: var(--primary-color); background: var(--surface-color); }
    tr:last-child td { border-bottom: 0; }
    .page-footer { text-align: center; color: var(--muted-text); font-size: .8em; padding-top: 24px; border-top: 1px solid var(--border-color); }
    .reading-tools {
      position: fixed; z-index: 20; bottom: max(12px, env(safe-area-inset-bottom)); left: 50%; transform: translateX(-50%);
      display: flex; align-items: center; gap: 7px; width: max-content; max-width: calc(100% - 20px);
      padding: 8px 10px; border: 1px solid var(--border-color); border-radius: 999px;
      background: var(--page-bg); color: var(--text-color); box-shadow: 0 6px 22px rgba(0,0,0,.16);
      font-size: 16px;
    }
    button { font: inherit; cursor: pointer; touch-action: manipulation; }
    .control { display: inline-flex; justify-content: center; align-items: center; min-width: 44px; min-height: 44px; padding: 6px 12px; border: 1px solid var(--border-color); border-radius: 999px; background: var(--surface-color); color: var(--primary-color); font-weight: 600; }
    .control:hover:not(:disabled) { background: var(--primary-color); color: var(--page-bg); }
    .control:disabled { opacity: .4; cursor: default; }
    #text-scale-value { min-width: 47px; text-align: center; direction: ltr; color: var(--muted-text); font-size: 14px; }
    .divider { height: 24px; border-inline-start: 1px solid var(--border-color); margin-inline: 3px; }
    #theme-icon { font-size: 23px; line-height: 1; }
    .skip-link { position: fixed; z-index: 50; top: -100px; right: 20px; background: var(--page-bg); padding: 12px 20px; border: 2px solid var(--primary-color); border-radius: 8px; }
    .skip-link:focus { top: 12px; }
    #image-zoom { width: min(94vw, 1400px); max-width: 94vw; max-height: 92dvh; padding: 18px; border: 1px solid var(--border-color); border-radius: 12px; background: var(--page-bg); color: var(--text-color); }
    #image-zoom::backdrop { background: rgba(0,0,0,.82); }
    .zoom-toolbar { display: flex; justify-content: space-between; gap: 12px; align-items: center; flex-wrap: wrap; padding-bottom: 14px; }
    #image-zoom-title { font-size: 18px; margin: 0; border: 0; padding: 0; flex: 1 1 180px; }
    .zoom-actions { display: flex; align-items: center; gap: 8px; }
    #image-zoom-content { direction: ltr; overflow: auto; max-height: 70dvh; }
    #image-zoom-content img { display: block; height: auto; margin-inline: auto; max-width: none; }
    #zoom-help { text-align: center; color: var(--muted-text); font-size: 14px; margin-top: 12px; }
    html.image-zoom-open { overflow: hidden; }
    @media (max-width: 760px) {
      body { padding-top: 12px; }
      .page-shell { width: calc(100% - 20px); padding: 28px 20px 24px; border-radius: 12px; }
      .panel { margin-bottom: 36px; }
      .cover { padding-bottom: 24px; }
      h1 { font-size: 1.65em; }
      h2 { font-size: 1.35em; }
      .toc-list { grid-template-columns: 1fr; }
      .components { columns: 1; }
      .image-placeholder { min-height: 190px; padding: 22px 16px; }
      .notice { padding: 16px; }
      th, td { padding: 12px; }
    }
    @media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } body { transition: none; } }
    @media print {
      :root, :root[data-theme="dark"] { color-scheme: light; --bg-color: white; --page-bg: white; --text-color: #222; --muted-text: #555; --primary-color: #005b99; --surface-color: #f7f7f7; --border-color: #ccc; --notice-bg: #f5f5f5; }
      body { padding: 0; }
      .page-shell { width: 100%; font-size: 12pt; padding: 0; border: 0; border-radius: 0; box-shadow: none; }
      .panel { margin-bottom: 24px; }
      .reading-tools, .back-link, .skip-link, #image-zoom { display: none !important; }
      .figure, .notice, tr { break-inside: avoid; }
      h2, h3 { break-after: avoid; }
      .image-placeholder { min-height: 130px; }
    }

    /* Offline code examples, kept left-to-right within the Arabic article. */
    .code-block {
      display: block; width: 100%; max-width: 100%; margin: 18px 0 22px; padding: 20px 24px;
      direction: ltr; text-align: left; unicode-bidi: isolate; overflow-x: auto;
      background: var(--surface-color); color: var(--text-color);
      border: 1px solid var(--border-color); border-radius: 10px;
      font-size: .9em; line-height: 1.7; tab-size: 2;
    }
    .code-block code { font-family: Consolas, 'Courier New', monospace; font-size: 1em; white-space: pre; }
    .code-block.has-line-numbers {
      display: grid; grid-template-columns: max-content minmax(0, 1fr); column-gap: 1em;
      font-family: Consolas, 'Courier New', monospace;
    }
    .code-block.has-line-numbers code { display: block; width: max-content; }
    .code-line-numbers {
      align-self: start; padding-right: 1em; border-right: 1px solid var(--border-color);
      color: var(--muted-text); text-align: right; user-select: none; pointer-events: none;
    }
    .code-line-numbers > span { display: block; }
    .code-line-numbers > span::before { content: attr(data-line); }
    .token.comment, .token.prolog, .token.doctype, .token.cdata { color: #617080; }
    .token.keyword, .token.directive, .token.directive-hash { color: #0068a6; }
    .token.number, .token.boolean, .token.constant { color: #a51d68; }
    .token.string, .token.char { color: #357400; }
    .token.function { color: #795000; }
    .token.operator, .token.punctuation { color: #4b5563; }
    :root[data-theme="dark"] .token.comment { color: #a1afc1; }
    :root[data-theme="dark"] .token.keyword,
    :root[data-theme="dark"] .token.directive,
    :root[data-theme="dark"] .token.directive-hash { color: #7dd3fc; }
    :root[data-theme="dark"] .token.number,
    :root[data-theme="dark"] .token.boolean,
    :root[data-theme="dark"] .token.constant { color: #f9a8d4; }
    :root[data-theme="dark"] .token.string,
    :root[data-theme="dark"] .token.char { color: #bef264; }
    :root[data-theme="dark"] .token.function { color: #fde68a; }
    :root[data-theme="dark"] .token.operator,
    :root[data-theme="dark"] .token.punctuation { color: #cbd5e1; }
    @media (max-width: 760px) { .code-block { padding: 14px; } }
    @media print { .code-block { white-space: pre-wrap; overflow: visible; } .code-block code { white-space: pre-wrap; overflow-wrap: anywhere; } }
    .inline-code {
      display: inline-block; direction: ltr; unicode-bidi: isolate;
      font-family: Consolas, 'Courier New', monospace; font-size: .95em;
      padding: 0 .3em; border-radius: 4px; background: var(--surface-color); color: var(--text-color);
      overflow-wrap: anywhere; max-width: 100%; vertical-align: baseline;
    }