/* ========== 设计令牌 ========== */
:root {
  /* 颜色 */
  --brand: #0FA3B1;
  --accent: #E3B23C;
  --bg: #F9FAFB;
  --card: #FFFFFF;
  --text: #1F2937;
  --text-secondary: #4B5563;
  --muted: #6B7280;
  --border: #E5E7EB;
  --success: #10B981;
  --error: #EF4444;
  --warning: #F59E0B;
  
  /* 阴影 */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  
  /* 间距 */
  --spacing-xs: 0.5rem;
  --spacing-sm: 0.75rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  
  /* 圆角 */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-full: 9999px;
  
  /* 过渡 */
  --transition: all 0.2s ease;
}

[data-theme="dark"] {
  --bg: #0B0F14;
  --card: #121821;
  --text: #E5E7EB;
  --text-secondary: #D1D5DB;
  --muted: #9CA3AF;
  --border: #1F2937;
}

/* ========== 基础重置 ========== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
}

/* 主题切换平滑过渡 */
html.theme-transitioning,
html.theme-transitioning *,
html.theme-transitioning *:before,
html.theme-transitioning *:after {
  transition: background-color 0.3s ease, 
              color 0.3s ease, 
              border-color 0.3s ease,
              box-shadow 0.3s ease !important;
  transition-delay: 0s !important;
}

/* ========== 排版 ========== */
h1 {
  font-size: 2.5rem;
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: var(--spacing-lg);
}

h2 {
  font-size: 1.75rem;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: var(--spacing-md);
}

h3 {
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: var(--spacing-sm);
}

p {
  font-size: 1rem;
  line-height: 1.6;
  margin-bottom: var(--spacing-md);
  color: var(--text-secondary);
}

a {
  color: var(--brand);
  text-decoration: none;
  transition: var(--transition);
}

a:hover {
  color: var(--accent);
}

/* ========== 容器 ========== */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

/* ========== 头部导航 ========== */
.header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(8px);
}

.nav-wrapper {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 70px;
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
}

.logo-icon {
  font-size: 1.5rem;
}

.nav-desktop {
  display: flex;
  gap: var(--spacing-xl);
}

.nav-link {
  color: var(--text);
  font-weight: 500;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-sm);
  transition: var(--transition);
}

.nav-link:hover {
  background: var(--bg);
  color: var(--brand);
}

.nav-tools {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

/* 语言切换 */
.lang-switcher {
  display: flex;
  gap: 0.25rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  padding: 0.25rem;
}

.lang-btn {
  background: transparent;
  border: none;
  border-radius: var(--radius-full);
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--muted);
}

.lang-btn:hover {
  color: var(--text);
}

.lang-btn.active {
  background: var(--brand);
  color: white;
}

.theme-toggle {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  width: 42px;
  height: 42px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition);
  font-size: 1.25rem;
}

.theme-toggle:hover {
  transform: scale(1.05);
}

[data-theme="light"] .theme-icon-dark,
[data-theme="dark"] .theme-icon-light {
  display: none;
}

.mobile-menu-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  width: 40px;
  height: 40px;
  position: relative;
}

.hamburger {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.hamburger::before,
.hamburger::after {
  content: '';
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  position: absolute;
  left: 0;
  transition: var(--transition);
}

.hamburger::before {
  top: -8px;
}

.hamburger::after {
  bottom: -8px;
}

.nav-mobile {
  display: none;
  flex-direction: column;
  gap: var(--spacing-sm);
  padding: var(--spacing-lg) 0;
  border-top: 1px solid var(--border);
}

.nav-mobile.active {
  display: flex;
}

.nav-link-mobile {
  display: block;
  padding: var(--spacing-md);
  color: var(--text);
  font-weight: 500;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}

.nav-link-mobile:hover {
  background: var(--bg);
  color: var(--brand);
}

/* ========== 主体 ========== */
.main {
  min-height: calc(100vh - 140px);
  padding: var(--spacing-2xl) 0;
}

/* ========== 卡片 ========== */
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

.card:hover {
  box-shadow: var(--shadow-md);
}

/* ========== 按钮 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: 1rem;
  font-weight: 600;
  border-radius: 14px;
  border: none;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
  line-height: 1;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: var(--brand);
  color: white;
}

.btn-primary:hover {
  background: #0d8a96;
  color: white;
}

.btn-secondary {
  background: var(--accent);
  color: white;
}

.btn-secondary:hover {
  background: #d4a134;
  color: white;
}

.btn-outline {
  background: transparent;
  border: 2px solid var(--brand);
  color: var(--brand);
}

.btn-outline:hover {
  background: var(--brand);
  color: white;
}

.btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
}

/* ========== 表单 ========== */
.form-group {
  margin-bottom: var(--spacing-lg);
}

.form-label {
  display: block;
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  color: var(--text);
}

.form-input,
.form-textarea {
  width: 100%;
  padding: var(--spacing-md);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--bg);
  color: var(--text);
  font-size: 1rem;
  font-family: inherit;
  transition: var(--transition);
}

.form-input:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--brand);
  box-shadow: 0 0 0 3px rgba(15, 163, 177, 0.1);
}

.form-textarea {
  min-height: 120px;
  resize: vertical;
}

.form-hint {
  display: block;
  margin-top: var(--spacing-xs);
  font-size: 0.875rem;
  color: var(--muted);
}

.char-counter {
  float: right;
  font-family: 'Monaco', monospace;
}

/* ========== Toast ========== */
.toast-container {
  position: fixed;
  top: var(--spacing-xl);
  right: var(--spacing-xl);
  z-index: 9999;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  max-width: 400px;
}

.toast {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--spacing-md) var(--spacing-lg);
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  animation: slideIn 0.3s ease;
}

@keyframes slideIn {
  from {
    transform: translateX(100%);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

.toast.success {
  border-left: 4px solid var(--success);
}

.toast.error {
  border-left: 4px solid var(--error);
}

.toast.warning {
  border-left: 4px solid var(--warning);
}

.toast-icon {
  font-size: 1.25rem;
}

.toast-message {
  flex: 1;
  font-size: 0.9375rem;
}

/* ========== 底部 ========== */
.footer {
  background: var(--card);
  border-top: 1px solid var(--border);
  padding: var(--spacing-xl) 0;
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--spacing-md);
}

.footer-text {
  color: var(--muted);
  font-size: 0.875rem;
  margin: 0;
}

.footer-links {
  display: flex;
  gap: var(--spacing-lg);
}

.footer-link {
  color: var(--muted);
  font-size: 0.875rem;
  transition: var(--transition);
}

.footer-link:hover {
  color: var(--brand);
}

/* ========== 响应式 ========== */
@media (max-width: 768px) {
  .nav-desktop {
    display: none;
  }
  
  .mobile-menu-toggle {
    display: block;
  }
  
  h1 {
    font-size: 2rem;
  }
  
  h2 {
    font-size: 1.5rem;
  }
  
  .container {
    padding: 0 var(--spacing-md);
  }
  
  .toast-container {
    right: var(--spacing-md);
    left: var(--spacing-md);
    max-width: none;
  }
  
  .footer-content {
    flex-direction: column;
    text-align: center;
  }
}

/* ========== 工具类 ========== */
.text-center {
  text-align: center;
}

.mt-1 { margin-top: var(--spacing-md); }
.mt-2 { margin-top: var(--spacing-lg); }
.mt-3 { margin-top: var(--spacing-xl); }
.mt-4 { margin-top: var(--spacing-2xl); }

.mb-1 { margin-bottom: var(--spacing-md); }
.mb-2 { margin-bottom: var(--spacing-lg); }
.mb-3 { margin-bottom: var(--spacing-xl); }
.mb-4 { margin-bottom: var(--spacing-2xl); }

.grid {
  display: grid;
  gap: var(--spacing-lg);
}

.grid-2 {
  grid-template-columns: repeat(2, 1fr);
}

.grid-3 {
  grid-template-columns: repeat(3, 1fr);
}

.grid-4 {
  grid-template-columns: repeat(4, 1fr);
}

@media (max-width: 768px) {
  .grid-2,
  .grid-3,
  .grid-4 {
    grid-template-columns: 1fr;
  }
}