/* ===== 页面整体布局 ===== */

body {
  display: flex;
  min-height: 100vh;
}

/* ===== 侧边导航 ===== */

.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--nav-width);
  height: 100vh;
  overflow-y: auto;
  padding: var(--space-8) var(--space-6);
  background: var(--color-bg);
  z-index: 100;
  transition: transform var(--duration-normal) var(--ease-out);
}

.nav-logo {
  font-size: var(--text-lg);
  font-weight: var(--weight-bold);
  color: var(--color-text);
  text-decoration: none;
  display: block;
  margin-bottom: var(--space-8);
  letter-spacing: -0.01em;
}

/* 树形目录 */

.nav-tree {
  display: flex;
  flex-direction: column;
}

.nav-item {
  display: block;
  padding: var(--space-3) 0;
  font-size: var(--text-base);
  color: var(--color-text-tertiary);
  text-decoration: none;
  line-height: var(--leading-tight);
  transition: color var(--duration-fast) var(--ease-out);
}

a.nav-item:hover {
  color: var(--color-text);
  text-decoration: none;
}

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

.nav-label {
  font-weight: var(--weight-normal);
  color: var(--color-text-tertiary);
  cursor: default;
}

/* 层级缩进 */
.nav-lv1 {
  border-top: 1px solid var(--color-border-light);
  padding-top: var(--space-4);
  padding-bottom: var(--space-4);
}

.nav-lv1:first-child {
  border-top: none;
  padding-top: 0;
}

.nav-lv2 {
  padding-left: var(--space-4);
  font-size: var(--text-sm);
  padding-top: var(--space-2);
  padding-bottom: var(--space-2);
}

.nav-lv3 {
  padding-left: var(--space-8);
  font-size: var(--text-sm);
  padding-top: var(--space-1);
  padding-bottom: var(--space-1);
}

.nav-lv4 {
  padding-left: var(--space-12);
  font-size: var(--text-sm);
  padding-top: var(--space-1);
  padding-bottom: var(--space-1);
}

/* ===== 主内容区 ===== */

.content {
  flex: 1;
  margin-left: var(--nav-width);
  padding: var(--space-12) var(--page-padding);
  min-height: 100vh;
}

.article {
  max-width: var(--content-max-width);
  margin: 0 auto;
}

/* ===== 页面底部导航（上一页/下一页） ===== */

.page-nav {
  display: flex;
  justify-content: space-between;
  gap: var(--space-4);
  margin-top: var(--space-20);
  padding-top: var(--space-8);
  border-top: 1px solid var(--color-border-light);
}

.page-nav-link {
  position: relative;
  display: flex;
  flex-direction: column;
  padding: var(--space-4) var(--space-5);
  text-decoration: none;
  max-width: 50%;
  isolation: isolate;
  transform: rotate(-0.5deg);
  transition: transform var(--duration-normal) var(--ease-out);
}

.page-nav-link::after {
  content: '';
  position: absolute;
  inset: 0;
  border: 2.8px solid rgba(0, 0, 0, 0.08);
  background: #1C1C1A;
  border-radius: 16px 10px 18px 8px;
  filter: url(#sketch);
  z-index: -1;
  transition: box-shadow var(--duration-normal) var(--ease-out);
}

.page-nav-link:hover {
  transform: rotate(0deg) translateY(-2px);
  text-decoration: none;
}

.page-nav-link:hover::after {
  box-shadow: 0 5px 16px rgba(0, 0, 0, 0.1);
}

.page-nav-link--next {
  margin-left: auto;
  text-align: right;
  transform: rotate(0.5deg);
}

.page-nav-link--next::after {
  border-radius: 10px 18px 8px 16px;
}

.page-nav-link--next:hover {
  transform: rotate(0deg) translateY(-2px);
}

.page-nav-label {
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  color: #FFFFFF;
  margin-bottom: var(--space-1);
}

.page-nav-title {
  font-size: var(--text-base);
  font-weight: var(--weight-bold);
  color: #FFFFFF;
}

/* ===== 移动端汉堡菜单 ===== */

.nav-toggle {
  display: none;
  position: fixed;
  top: var(--space-4);
  left: var(--space-4);
  z-index: 200;
  width: 40px;
  height: 40px;
  border: none;
  background: transparent;
  cursor: pointer;
  align-items: center;
  justify-content: center;
  isolation: isolate;
  transform: rotate(-0.7deg);
  transition: transform var(--duration-normal) var(--ease-out);
}

.nav-toggle::after {
  content: '';
  position: absolute;
  inset: 0;
  background: var(--color-surface);
  border: 2.8px solid rgba(0, 0, 0, 0.08);
  border-radius: 16px 10px 18px 8px;
  filter: url(#sketch);
  z-index: -1;
  transition: box-shadow var(--duration-normal) var(--ease-out);
}

.nav-toggle:hover {
  transform: rotate(0deg) translateY(-1px);
}

.nav-toggle:hover::after {
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.nav-toggle-icon {
  width: 18px;
  height: 2px;
  background: var(--color-text);
  position: relative;
  transition: background var(--duration-fast);
}

.nav-toggle-icon::before,
.nav-toggle-icon::after {
  content: '';
  position: absolute;
  width: 18px;
  height: 2px;
  background: var(--color-text);
  left: 0;
  transition: transform var(--duration-normal) var(--ease-out);
}

.nav-toggle-icon::before { top: -6px; }
.nav-toggle-icon::after  { top: 6px; }

/* 打开状态 */
.nav-toggle.is-active .nav-toggle-icon { background: transparent; }
.nav-toggle.is-active .nav-toggle-icon::before {
  transform: rotate(45deg);
  top: 0;
}
.nav-toggle.is-active .nav-toggle-icon::after {
  transform: rotate(-45deg);
  top: 0;
}

/* 遮罩 */
.nav-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.3);
  z-index: 90;
}

/* ===== 响应式 ===== */

@media (max-width: 1024px) {
  .nav-toggle {
    display: flex;
  }

  .site-nav {
    transform: translateX(-100%);
    width: 280px;
    box-shadow: var(--shadow-lg);
  }

  .site-nav.is-open {
    transform: translateX(0);
  }

  .nav-overlay.is-open {
    display: block;
  }

  .content {
    margin-left: 0;
    padding-top: var(--space-16);
  }
}

@media (max-width: 640px) {
  .page-nav {
    flex-direction: column;
  }

  .page-nav-link {
    max-width: 100%;
  }

  .page-nav-link--next {
    text-align: left;
  }
}