/* 版本: 2026.1.10 - 优化版 */

/* ========== CSS 变量 (主题控制) ========== */
:root {
  --color-bg-primary: #f8f5f0;
  --color-bg-card: #ffffff;
  --color-bg-header: #ffffff;
  --color-bg-footer: #f5f5f5;
  --color-bg-toolbar: #f8f5f0;
  --color-text-primary: #333333;
  --color-text-secondary: #666666;
  --color-text-muted: #999999;
  --color-text-light: #ffffff;
  --color-text-link: #2563eb;
  --color-text-link-hover: #3b82f6;
  --color-border: #e0d8c8;
  --color-accent: #2563eb;
  --color-accent-hover: #3b82f6;
  --font-size-base: 18px;
  --font-family: -apple-system, BlinkMacSystemFont, "Microsoft YaHei", "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --line-height: 1.8;
  --transition-speed: 0.3s;
  --container-max-width: 1200px;
}
body.night-mode {
  --color-bg-primary: #1a1a1a;
  --color-bg-card: #252525;
  --color-bg-header: #2d2d2d;
  --color-bg-footer: #151515;
  --color-bg-toolbar: #2d2d2d;
  --color-text-primary: #e8e6e3;
  --color-text-secondary: #b8b6b3;
  --color-text-muted: #888888;
  --color-text-light: #f0f0f0;
  --color-text-link: #60a5fa;
  --color-text-link-hover: #93c5fd;
  --color-border: #404040;
  --color-accent: #60a5fa;
  --color-accent-hover: #93c5fd;
}
body.font-size-small { --font-size-base: 16px; }
body.font-size-normal { --font-size-base: 18px; }
body.font-size-large { --font-size-base: 20px; }
body.font-size-xlarge { --font-size-base: 22px; }

/* ========== 重置与基础样式 ========== */
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: var(--line-height);
  color: var(--color-text-primary);
  background-color: var(--color-bg-primary);
  transition: background-color var(--transition-speed), color var(--transition-speed);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 20px;
}
a { color: var(--color-text-link); text-decoration: none; transition: color var(--transition-speed); }
a:hover { color: var(--color-text-link-hover); }
button { cursor: pointer; border: none; background: none; font-family: inherit; transition: all var(--transition-speed); }

/* ========== 头部样式 ========== */
.site-header {
  background-color: var(--color-bg-header);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
  padding: 12px 0;
}
.header-main {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  flex-wrap: nowrap;
}
.header-left {
  display: flex;
  align-items: center;
  gap: 15px;
  flex-shrink: 0;
}
.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text-primary);
  display: flex;
  align-items: center;
  gap: 10px;
  white-space: nowrap;
}
.logo:hover { color: var(--color-accent); }
.lang-btn {
  padding: 6px 12px;
  border-radius: 4px;
  font-size: 0.9rem;
  border: 1px solid var(--color-border);
  background-color: var(--color-bg-card);
  color: var(--color-text-secondary);
  min-width: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  white-space: nowrap;
}
.lang-btn:hover {
  background-color: var(--color-accent);
  color: white;
  border-color: var(--color-accent);
}
.header-center {
  display: flex;
  flex: 1;
  justify-content: center;
  max-width: 400px;
}
.search-form { display: flex; width: 100%; }
.search-input {
  flex: 1;
  padding: 8px 12px;
  border: 1px solid var(--color-border);
  border-right: none;
  border-radius: 4px 0 0 4px;
  font-size: 0.9rem;
  background-color: var(--color-bg-card);
  color: var(--color-text-primary);
  transition: border-color var(--transition-speed);
  min-width: 150px;
}
.search-input:focus { outline: none; border-color: var(--color-accent); }
.search-btn {
  padding: 8px 15px;
  background-color: var(--color-accent);
  color: white;
  border-radius: 0 4px 4px 0;
  display: flex;
  align-items: center;
  justify-content: center;
}
.search-btn:hover { background-color: var(--color-accent-hover); }
.header-right {
  display: flex;
  align-items: center;
  gap: 20px;
  flex-shrink: 0;
  justify-content: flex-end;
}
.main-nav {
  display: flex;
  align-items: center;
  gap: 20px;
  font-size: 1rem;
}
.main-nav .nav-link {
  padding: 6px 12px;
  color: var(--color-text-secondary);
  display: flex;
  align-items: center;
  gap: 6px;
  white-space: nowrap;
}
.main-nav .nav-link:hover { color: var(--color-accent); }
.menu-toggle {
  display: none; /* 默认隐藏，在媒体查询中控制显示 */
  width: 40px;
  height: 40px;
  border-radius: 4px;
  border: 1px solid var(--color-border);
  background-color: var(--color-bg-card);
  color: var(--color-text-secondary);
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
}
.menu-toggle:hover {
  background-color: var(--color-accent);
  color: white;
  border-color: var(--color-accent);
}
.mobile-menu {
  display: none;
  background-color: var(--color-bg-card);
  border-radius: 4px;
  border: 1px solid var(--color-border);
  margin-top: 10px;
  overflow: hidden;
  animation: slideDown 0.3s ease;
  font-size: 1rem;
}
@keyframes slideDown {
  from { opacity: 0; transform: translateY(-10px); }
  to { opacity: 1; transform: translateY(0); }
}
.mobile-menu.show { display: block; }
.mobile-nav-link {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 20px;
  color: var(--color-text-secondary);
  border-bottom: 1px solid var(--color-border);
  text-decoration: none;
}
.mobile-nav-link:last-child { border-bottom: none; }
.mobile-nav-link:hover {
  background-color: var(--color-accent);
  color: white;
}

/* ========== 底部 ========== */
.site-footer {
  background-color: var(--color-bg-footer);
  color: var(--color-text-primary);
  padding: 20px 0;
  margin-top: auto;
  text-align: center;
  border-top: 1px solid var(--color-border);
}
.footer-inner p { line-height: 1.6; opacity: 0.8; font-size: 0.9rem; }

/* ========== 功能按钮 ========== */
.theme-btn, #gotop {
  position: fixed;
  right: 20px;
  width: 50px;
  height: 50px;
  border-radius: 50%;
  background-color: var(--color-accent);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
  opacity: 0.9;
  z-index: 100;
  transition: opacity var(--transition-speed), transform var(--transition-speed);
}
.theme-btn { bottom: 20px; }
.theme-btn:hover { opacity: 1; transform: translateY(-2px); box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3); }
#gotop {
  bottom: 80px;
  display: none;
}
#gotop.show { display: flex; }
#gotop:hover { opacity: 1; transform: translateY(-2px); box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3); }

/* ========== 响应式设计 ========== */
/* 980px-641px 布局 */
@media (max-width: 979px) and (min-width: 641px) {
  .container { padding: 0 15px; }
  .header-center { max-width: none; }
  .main-nav { display: none; }
  .menu-toggle { display: flex; } /* 在此断点显示菜单按钮 */
  .theme-btn, #gotop { width: 45px; height: 45px; }
  #gotop { bottom: 75px; }
}
/* 640px以下布局 */
@media (max-width: 640px) {
  .container { padding: 0 15px; }
  .header-main { flex-wrap: wrap; }
  .header-left { flex: 1; gap: 10px; }
  .header-center { order: 3; min-width: 340px; max-width: 100%; justify-content: center; }
  .search-form { width: 100%; }
  .main-nav { display: none; }
  .menu-toggle { display: flex; } /* 在此断点显示菜单按钮 */
  .mobile-menu { order: 4; width: 100%; margin-top: 10px; }
  .theme-btn, #gotop { width: 45px; height: 45px; }
  #gotop { bottom: 75px; }
  .logo { font-size: 1.3rem; }
  .lang-btn { padding: 5px 8px; min-width: 35px; }
  .search-input { min-width: 100px; }
}
/* 宽屏布局 (确保折叠菜单不显示) */
@media (min-width: 980px) {
  .menu-toggle, .mobile-menu { display: none; }
}