/* ====== 基础排版 ====== */
* { box-sizing: border-box; }
html, body {
  height: 100%;
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
               "Microsoft YaHei", "Hiragino Sans GB", sans-serif;
  background: linear-gradient(180deg, var(--bg-grad-1) 0%, var(--bg-grad-2) 100%);
  color: var(--text);
  font-size: 14px;
  line-height: 1.6;
  transition: background 0.3s, color 0.3s;
}
#app { min-height: 100vh; display: flex; flex-direction: column; }

/* ====== 通用元素 ====== */
button {
  font: inherit;
  color: inherit;
  background: var(--btn-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 6px 14px;
  cursor: pointer;
  transition: all 0.15s;
}
button:hover:not(:disabled) {
  background: var(--hover-bg);
  border-color: var(--accent);
}
button:active:not(:disabled) { transform: scale(0.97); }
button:disabled { opacity: 0.4; cursor: not-allowed; }
button.primary {
  background: var(--accent);
  color: #fff;
  border: none;
  font-weight: 600;
}
button.primary:hover:not(:disabled) { filter: brightness(0.9); }
button.ghost { background: transparent; }

input, textarea, select {
  font: inherit;
  color: var(--text);
  background: var(--input-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 6px 10px;
  transition: border-color 0.15s;
}
input:focus, textarea:focus, select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.15);
}

h1, h2, h3, h4, h5, h6 { margin: 1.4em 0 0.6em; font-weight: 700; line-height: 1.3; }
h1 { font-size: 28px; color: var(--accent); }
h2 { font-size: 22px; color: var(--accent2); }
h3 { font-size: 18px; }
h4 { font-size: 16px; color: var(--muted); }

p { margin: 0.6em 0; }
strong { color: var(--accent); font-weight: 600; }

a { color: var(--accent2); text-decoration: none; }
a:hover { text-decoration: underline; }

code {
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  font-size: 0.9em;
  background: var(--code-bg);
  color: var(--code-text);
  padding: 2px 6px;
  border-radius: 4px;
}
pre {
  background: var(--code-bg);
  color: var(--code-text);
  padding: 14px 16px;
  border-radius: 8px;
  overflow-x: auto;
  border: 1px solid var(--border);
}
pre code { background: transparent; padding: 0; }

blockquote {
  margin: 1em 0;
  padding: 12px 18px;
  background: var(--blockquote-bg);
  border-left: 4px solid var(--blockquote-border);
  border-radius: 6px;
  color: var(--text);
}
blockquote p { margin: 0; }

hr { border: none; border-top: 1px solid var(--border); margin: 2em 0; }

table {
  border-collapse: collapse;
  margin: 1em 0;
  width: 100%;
  font-variant-numeric: tabular-nums;
}
th, td {
  padding: 8px 12px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}
th { background: var(--panel2); font-weight: 600; }

img { max-width: 100%; height: auto; border-radius: 8px; }

/* ====== AppShell：header + sidebar + main 三段布局 ====== */
header {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 12px 20px;
  background: var(--panel);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 100;
}
header .brand {
  font-weight: 800;
  font-size: 16px;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  white-space: nowrap;
}
header .spacer { flex: 1; }
header .progress-bar {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
}
header .progress-stat {
  display: flex;
  flex-direction: column;
  font-size: 10px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  line-height: 1.2;
}
header .progress-stat .val {
  font-size: 14px;
  font-weight: 700;
  color: var(--text);
  font-variant-numeric: tabular-nums;
}
header .progress-track {
  width: 120px;
  height: 6px;
  background: var(--border);
  border-radius: 3px;
  overflow: hidden;
}
header .progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  transition: width 0.4s;
}
header select {
  padding: 4px 8px;
  font-size: 13px;
  border-radius: 6px;
}

.app-body {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 0;
  flex: 1;
  min-height: 0;
}

/* ====== 侧边栏 ====== */
aside.sidebar {
  background: var(--panel);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  padding: 16px 12px;
  position: sticky;          /* 悬浮：滚动时跟随视口 */
  top: 56px;                 /* 避开 header (~50px) */
  align-self: start;         /* grid 子项必须，否则 sticky 失效 */
  max-height: calc(100vh - 56px);  /* 防止内容超视口 */
}
.sidebar h3 {
  font-size: 11px;
  font-weight: 700;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.8px;
  margin: 8px 0 6px;
  padding: 0 8px;
}
.sidebar .chapter-link {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: 8px;
  margin-bottom: 4px;
  color: var(--text);
  cursor: pointer;
  transition: background 0.15s;
  font-size: 13px;
  line-height: 1.3;
}
.sidebar .chapter-link:hover {
  background: var(--hover-bg);
  text-decoration: none;
}
.sidebar .chapter-link.active {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.15), rgba(14, 165, 233, 0.15));
  border-left: 3px solid var(--accent);
  padding-left: 9px;
  font-weight: 600;
}
.sidebar .chapter-link.locked { opacity: 0.45; cursor: not-allowed; }
.sidebar .chapter-link.completed .chapter-num { background: var(--accent); color: #fff; }
.sidebar .chapter-num {
  flex: 0 0 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--panel2);
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 11px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}
.sidebar .chapter-title { flex: 1; }
.sidebar .chapter-badge {
  font-size: 9px;
  padding: 2px 6px;
  background: var(--accent2);
  color: #fff;
  border-radius: 4px;
  font-weight: 700;
  letter-spacing: 0.5px;
}

/* Sidebar 底部：重置按钮（占满宽度，弱化样式） */
.sidebar-footer {
  margin-top: 32px;
  padding-top: 16px;
  border-top: 1px dashed var(--border);
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.sidebar-footer .reset-btn {
  width: 100%;
  background: transparent;
  color: var(--muted);
  border: 1px dashed var(--border);
  border-radius: 8px;
  padding: 8px 12px;
  font-size: 12px;
  cursor: pointer;
  transition: all 0.15s ease;
  font-family: inherit;
}
.sidebar-footer .reset-btn:hover {
  color: #fff;
  background: var(--accent);
  border-color: var(--accent);
  border-style: solid;
}

/* 调试弹窗 */
.debug-modal {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.55);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
}
.debug-modal-content {
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 12px;
  max-width: 720px;
  width: 90%;
  max-height: 80vh;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}
.debug-modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
}
.debug-modal-header h3 {
  margin: 0;
  font-size: 16px;
}
.debug-close {
  background: transparent;
  border: none;
  color: var(--muted);
  font-size: 24px;
  cursor: pointer;
  line-height: 1;
}
.debug-close:hover { color: var(--text); }
.debug-pre {
  margin: 0;
  padding: 16px;
  overflow: auto;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 12px;
  line-height: 1.6;
  white-space: pre;
}

/* ====== 主内容区 ====== */
main.content {
  overflow-y: auto;
  padding: 32px 48px;
  max-width: 100%;
}
main.content > * { max-width: 900px; margin: 0 auto; }

/* ====== 章节页面 ====== */
.chapter-header {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding-bottom: 16px;
  margin-bottom: 16px;
  border-bottom: 1px solid var(--border);
}
.chapter-header .chapter-num {
  font-size: 12px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-weight: 700;
}
.chapter-header h1 {
  margin: 0;
  color: var(--text);
}
.chapter-header .chapter-summary {
  color: var(--muted);
  font-size: 14px;
}
.chapter-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 32px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
}

/* ====== 欢迎页 ====== */
.home-hero {
  text-align: center;
  padding: 40px 20px;
}
.home-hero h1 {
  font-size: 36px;
  margin-bottom: 12px;
}
.home-hero .tagline {
  font-size: 16px;
  color: var(--muted);
  max-width: 600px;
  margin: 0 auto 24px;
}
.home-hero .stats {
  display: flex;
  gap: 32px;
  justify-content: center;
  flex-wrap: wrap;
  margin: 24px 0;
}
.home-hero .stat {
  text-align: center;
}
.home-hero .stat .val {
  font-size: 32px;
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
.home-hero .stat .lbl {
  font-size: 11px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
  margin-top: 32px;
}
.chapter-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
  cursor: pointer;
  transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
}
.chapter-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  border-color: var(--accent);
  text-decoration: none;
}
.chapter-card .num {
  font-size: 11px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-weight: 700;
}
.chapter-card h3 {
  margin: 6px 0 8px;
  color: var(--text);
  font-size: 16px;
}
.chapter-card p {
  color: var(--muted);
  font-size: 13px;
  margin: 0;
}
.chapter-card.completed {
  border-left: 3px solid var(--accent);
}

/* ====== Toast ====== */
.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--text);
  color: var(--bg);
  padding: 10px 20px;
  border-radius: 8px;
  box-shadow: var(--shadow-lg);
  z-index: 1000;
  font-size: 13px;
  font-weight: 500;
  animation: toastIn 0.3s, toastOut 0.3s 1.7s;
}
@keyframes toastIn { from { opacity: 0; transform: translate(-50%, 20px); } to { opacity: 1; transform: translate(-50%, 0); } }
@keyframes toastOut { to { opacity: 0; transform: translate(-50%, 20px); } }

/* ====== 响应式 ====== */
@media (max-width: 768px) {
  .app-body { grid-template-columns: 1fr; }
  aside.sidebar {
    border-right: none;
    border-bottom: 1px solid var(--border);
    max-height: 200px;
    position: static;        /* 移动端不悬浮 */
  }
  main.content { padding: 20px; }
  header { padding: 10px 14px; flex-wrap: wrap; }
  header .progress-bar { font-size: 11px; }
  header .progress-track { width: 80px; }
  .home-hero h1 { font-size: 26px; }
}