/* 基础变量与主题 */
:root {
  --bg: #ffffff;
  --fg: #111111;
  --muted: #6b7280;
  --border: #e5e7eb;
  --primary: #111827;
  --accent: #9ca3af; /* 链路强调色，可用于边框/描边 */
  --active-bg: #f1f5f9; /* 侧栏选中态（浅色） */
  --sidebar-bg: #f9fafb;
  --sidebar-fg: #111827;
  --link: #2563eb;
  --code-bg: #f3f4f6;
  --shadow: 0 8px 24px rgba(0,0,0,0.08);
}

@media (prefers-color-scheme: dark) {
  html[data-theme="auto"] {
    color-scheme: dark;
  }
}

html[data-theme="dark"] {
  --bg: #121317; /* 文本区域背景 */
  --fg: #e5e7eb;
  --muted: #9aa4b2;
  --border: #292b31;
  --primary: #f9fafb;
  --accent: #9ca3af;
  --active-bg: #1a1c1f; /* 侧栏选中态（深色） */
  --sidebar-bg: #0D0F11; /* 导航背景 */
  --sidebar-fg: #e5e7eb;
  --link: #cbd5e1;
  --code-bg: #0b1220;
  --shadow: 0 8px 24px rgba(0,0,0,0.4);
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 16px/1.6 -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Inter,Helvetica,Arial,"Apple Color Emoji","Segoe UI Emoji";
  text-rendering: optimizeLegibility;
  color-scheme: light dark; /* 使用系统标准滚动条 */
}

.app { display: flex; min-height: 100vh; }

/* 侧边栏 */
.sidebar {
  width: 300px;
  flex: 0 0 300px;
  background: var(--sidebar-bg);
  color: var(--sidebar-fg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  position: sticky;
  top: 0;
  height: 100vh;
  padding: 16px 12px;
  color-scheme: light dark; /* 侧栏滚动条随系统/主题 */
  overflow: auto; /* 标准系统滚动条 */
}

.brand { display: flex; align-items: center; gap: 12px; padding: 8px 8px 16px 8px; }
.brand-logo { width: 40px; height: 40px; border-radius: 10px; }
.brand-meta { display: flex; flex-direction: column; }
.brand-name { font-weight: 700; letter-spacing: .2px; }
.brand-tag { font-size: 12px; color: var(--muted); }

.nav { overflow: auto; padding: 8px; flex: 1; scrollbar-width: thin; scrollbar-color: var(--scroll-thumb) transparent; }
/* Firefox 变量 */
:root { --scroll-thumb: rgba(0,0,0,.28); }
html[data-theme="dark"] { --scroll-thumb: rgba(255,255,255,.28); }
/* WebKit 系 */
.nav::-webkit-scrollbar { width: 10px; height: 10px; background: transparent; }
.nav::-webkit-scrollbar-thumb { background-color: var(--scroll-thumb); border-radius: 8px; border: 2px solid transparent; background-clip: padding-box; }
.nav::-webkit-scrollbar-track { background: transparent; }
/* 悬停增强，对比更明显 */
.nav:hover::-webkit-scrollbar-thumb { background-color: color-mix(in srgb, var(--scroll-thumb), #000 15%); }
html[data-theme="dark"] .nav:hover::-webkit-scrollbar-thumb { background-color: color-mix(in srgb, var(--scroll-thumb), #fff 15%); }
/* 不交互时弱化 */
.nav:not(:hover)::-webkit-scrollbar-thumb { background-color: transparent; }
.nav-section-title { font-size: 12px; letter-spacing: .4px; text-transform: uppercase; color: var(--muted); margin: 16px 8px 6px; }
.nav-list { list-style: none; margin: 0; padding: 0; }
.nav-item { margin: 2px 0; }
.nav-link {
  display: block;
  padding: 8px 10px;
  border-radius: 8px;
  color: inherit;
  text-decoration: none;
}
.nav-link:hover { background: rgba(0,0,0,.04); }
html[data-theme="dark"] .nav-link:hover { background: rgba(255,255,255,.06); }
.nav-link.active { background: var(--active-bg); color: var(--fg); }

.sidebar-footer { display: none; }

/* 顶栏与主区域 */
.content-wrap { display: flex; flex-direction: column; flex: 1; min-width: 0; }
.topbar {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; justify-content: space-between;
  padding: 10px 14px; border-bottom: 1px solid var(--border);
  background: var(--bg); backdrop-filter: saturate(150%) blur(6px);
  -webkit-backdrop-filter: saturate(150%) blur(6px);
}
.icon-btn { background: transparent; border: 1px solid var(--border); color: inherit; border-radius: 8px; padding: 8px 10px; cursor: pointer; display: inline-flex; align-items: center; justify-content: center; }
.icon-btn:hover { background: rgba(0,0,0,.04); }
html[data-theme="dark"] .icon-btn:hover { background: rgba(255,255,255,.06); }
.icon-btn .icon { width: 24px; height: 24px; display: block; }
.brand-compact { display: none; align-items: center; gap: 10px; }
.brand-compact .brand-logo { width: 26px; height: 26px; }

main { display: block; }
.content { max-width: 920px; padding: 24px 24px 80px; margin: 0 auto; }
.content img { max-width: 100%; height: auto; border-radius: 8px; box-shadow: var(--shadow); }
.content h1, .content h2, .content h3, .content h4 { line-height: 1.25; }
.content h1 { font-size: 32px; margin: 12px 0 16px; }
.content h2 { font-size: 24px; margin: 24px 0 12px; }
.content h3 { font-size: 20px; margin: 18px 0 10px; }
.content p { margin: 0 0 12px; }
.content a { color: var(--link); }
.content pre { background: var(--code-bg); padding: 14px; border-radius: 10px; overflow: auto; }
.content code { font-family: ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,monospace; font-size: 85%; }
.content blockquote { border-left: 3px solid var(--border); padding-left: 12px; color: var(--muted); margin: 12px 0; }

/* 进度按钮 */
.progress-btn {
  position: fixed; right: 18px; bottom: 18px; z-index: 40;
  width: 48px; height: 48px; border-radius: 12px;
  border: none; background: var(--bg); color: var(--fg);
  box-shadow: 0 6px 18px rgba(0,0,0,.12), inset 0 1px 0 rgba(255,255,255,.06);
  cursor: pointer; display: grid; place-items: center;
  transition: transform .15s ease, box-shadow .2s ease;
}
.progress-btn:hover { transform: translateY(-1px); box-shadow: 0 8px 22px rgba(0,0,0,.18), inset 0 1px 0 rgba(255,255,255,.08); }
.progress-btn:active { transform: translateY(0); }
.progress-btn .arrow { position: relative; z-index: 2; font-weight: 800; font-size: 18px; }
.progress-btn::before { content: ""; position: absolute; inset: -2px; border-radius: 14px; background: conic-gradient(from 0deg, var(--accent) var(--progress,0%), transparent 0%); -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0); -webkit-mask-composite: xor; mask-composite: exclude; padding: 2px; filter: drop-shadow(0 4px 10px rgba(0,0,0,.14)); }
.progress-btn::after { content: ""; position: absolute; inset: 0; border-radius: 12px; background: linear-gradient(180deg, rgba(0,0,0,.04), rgba(0,0,0,0)); pointer-events: none; }
.progress-btn.hidden { opacity: 0; pointer-events: none; transform: translateY(6px); }

/* 背景遮罩（移动端侧栏） */
.backdrop { position: fixed; inset: 0; background: rgba(0,0,0,.3); opacity: 0; visibility: hidden; transition: .2s; z-index: 25; }
.backdrop.show { opacity: 1; visibility: visible; }

/* 响应式 */
@media (max-width: 1024px) {
  .sidebar { width: 280px; flex-basis: 280px; }
}

@media (max-width: 860px) {
  .sidebar { position: fixed; left: 0; top: 0; height: 100dvh; transform: translateX(-100%); transition: transform .25s ease; z-index: 30; }
  .sidebar.open { transform: translateX(0); }
  .brand-compact { display: none; }
  /* 仅窄屏显示汉堡 */
  #menuToggle { display: inline-flex; }
  .content { padding: 18px 16px 80px; }
}

@media (min-width: 861px) {
  /* 宽屏隐藏汉堡 */
  #menuToggle { display: none; }
  /* 右上角吸附操作区，确保主题按钮始终在右侧 */
  .topbar { justify-content: flex-end; }
}