/* ============================================================
 * 全局侧栏 — 纯字排版，零图标，分区编号 + 中文标
 * --------------------------------------------------------------
 * 核心视觉刻画：
 *   - 分区头：Fraunces 衬线斜体 + 微小分区编号 (01/02/03)，与正文 Inter 形成强烈反差
 *   - 二级条目：纯文字 14px，hover 仅文字颜色变化，active 时左侧 2px 竖线
 *   - 不使用 hover 背景色块或图标 → 让信息密度专注于"标签文字"本身
 * ============================================================ */

.t-sidebar {
  width: 220px;
  height: 100%;
  display: flex;
  flex-direction: column;
  padding: 28px 0 16px;
  background: #ffffff;
  border-right: 1px solid rgba(15, 23, 42, 0.06);
  font-family: var(--font-body);
  color: #1d1d1f;
  overflow-y: auto;
  flex-shrink: 0;
}

/* ===== 分区列表 ===== */
.t-sidebar__zones {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 28px;
  flex: 1;
}

.t-zone {
  display: flex;
  flex-direction: column;
}

/* —— 分区头：序号 + 中文标 —— */
.t-zone__head {
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding: 0 24px;
  margin-bottom: 8px;
}

.t-zone__serial {
  font-family: var(--font-serif);
  font-style: italic;
  font-weight: 300;
  font-size: 22px;
  line-height: 1;
  color: rgba(15, 23, 42, 0.32);
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.02em;
  /* Fraunces 可选项：optical sizing 在不同字号下自动调整笔画粗细 */
  font-optical-sizing: auto;
}

.t-zone__label {
  font-family: var(--font-body);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: rgba(15, 23, 42, 0.55);
}

/* ===== 二级条目 ===== */
.t-zone__items {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
}

.t-item {
  position: relative;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 24px;
  font-size: 14px;
  font-weight: 500;
  color: rgba(15, 23, 42, 0.72);
  cursor: pointer;
  user-select: none;
  outline: none;
  transition: color 120ms ease;
}

.t-item:hover,
.t-item:focus-visible {
  color: #0f172a;
}

.t-item:focus-visible {
  /* 不用粗暴 outline，用左边竖线作为焦点提示 */
  background: rgba(15, 23, 42, 0.03);
}

/* 左侧竖线：active 时显示 */
.t-item__rail {
  position: absolute;
  left: 0;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: transparent;
  border-radius: 0 2px 2px 0;
  transition: background-color 160ms ease;
}

.t-item.is-active {
  color: #0f172a;
  font-weight: 700;
}

.t-item.is-active .t-item__rail {
  background: #0f172a;
}

/* 标签 */
.t-item__label {
  flex: 1;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Beta 微章 */
.t-item__badge {
  font-family: var(--font-mono);
  font-size: 9px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 2px 6px;
  border-radius: 3px;
  background: rgba(15, 23, 42, 0.06);
  color: rgba(15, 23, 42, 0.55);
  flex-shrink: 0;
}

.t-item.is-active .t-item__badge {
  background: #0f172a;
  color: #ffffff;
}

/* ===== 底部主题切换 ===== */
.t-sidebar__foot {
  margin-top: 16px;
  padding: 16px 24px 0;
  border-top: 1px solid rgba(15, 23, 42, 0.06);
}

.t-theme {
  display: flex;
  align-items: center;
  gap: 8px;
  width: 100%;
  padding: 0;
  border: none;
  background: transparent;
  cursor: pointer;
  font-family: var(--font-body);
  font-size: 13px;
  color: rgba(15, 23, 42, 0.55);
  transition: color 120ms ease;
}

.t-theme:hover {
  color: #0f172a;
}

.t-theme__dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: linear-gradient(135deg, #fbbf24, #f97316);
  box-shadow: 0 0 0 2px rgba(251, 191, 36, 0.18);
  transition: background 200ms ease, box-shadow 200ms ease;
}

.t-theme__dot.is-night {
  background: linear-gradient(135deg, #1e293b, #475569);
  box-shadow: 0 0 0 2px rgba(71, 85, 105, 0.22);
}

/* ===== 夜间主题适配 ===== */
.app-container.theme-night .t-sidebar {
  background: #0b0f1a;
  border-right-color: rgba(255, 255, 255, 0.06);
  color: #e2e8f0;
}

.app-container.theme-night .t-zone__serial {
  color: rgba(226, 232, 240, 0.32);
}

.app-container.theme-night .t-zone__label {
  color: rgba(226, 232, 240, 0.5);
}

.app-container.theme-night .t-item {
  color: rgba(226, 232, 240, 0.7);
}

.app-container.theme-night .t-item:hover,
.app-container.theme-night .t-item:focus-visible,
.app-container.theme-night .t-item.is-active {
  color: #f8fafc;
}

.app-container.theme-night .t-item:focus-visible {
  background: rgba(255, 255, 255, 0.04);
}

.app-container.theme-night .t-item.is-active .t-item__rail {
  background: #f8fafc;
}

.app-container.theme-night .t-item__badge {
  background: rgba(255, 255, 255, 0.08);
  color: rgba(226, 232, 240, 0.65);
}

.app-container.theme-night .t-item.is-active .t-item__badge {
  background: #f8fafc;
  color: #0b0f1a;
}

.app-container.theme-night .t-sidebar__foot {
  border-top-color: rgba(255, 255, 255, 0.06);
}

.app-container.theme-night .t-theme {
  color: rgba(226, 232, 240, 0.55);
}

.app-container.theme-night .t-theme:hover {
  color: #f8fafc;
}

/* ===== 响应式：窄屏折叠（仅显示分区编号） ===== */
@media (max-width: 960px) {
  .t-sidebar {
    width: 64px;
  }
  .t-zone__head {
    padding: 0 12px;
    gap: 0;
    flex-direction: column;
    align-items: center;
    margin-bottom: 4px;
  }
  .t-zone__label {
    display: none;
  }
  .t-item {
    padding: 8px 12px;
    justify-content: center;
  }
  .t-item__label {
    display: none;
  }
  .t-item__badge {
    display: none;
  }
  .t-item.is-active::after {
    /* 折叠态用一个圆点表示 active */
    content: '';
    position: absolute;
    right: 8px;
    top: 50%;
    width: 4px;
    height: 4px;
    border-radius: 50%;
    background: currentColor;
    transform: translateY(-50%);
  }
  .t-theme__label {
    display: none;
  }
  .t-sidebar__foot {
    padding: 16px 12px 0;
  }
}