:root {
  --primary: #4CAF50;
  --primary-light: #81C784;
  --primary-dark: #388E3C;
  --secondary: #FF9800;
  --secondary-light: #FFB74D;
  --danger: #F44336;
  --danger-light: #FFCDD2;
  --success: #4CAF50;
  --success-light: #C8E6C9;
  --warning: #FFC107;
  --info: #2196F3;
  
  --bg-primary: #FFFFFF;
  --bg-secondary: #F5F5F5;
  --bg-card: #FFFFFF;
  
  --text-primary: #212121;
  --text-secondary: #757575;
  --text-hint: #BDBDBD;
  --text-white: #FFFFFF;
  
  --border-color: #E0E0E0;
  --shadow: 0 2px 8px rgba(0,0,0,0.1);
  --shadow-lg: 0 4px 16px rgba(0,0,0,0.15);
  
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --font-size-xs: 12px;
  --font-size-sm: 14px;
  --font-size-base: 16px;
  --font-size-lg: 18px;
  --font-size-xl: 24px;
  --font-size-xxl: 32px;
  
  --spacing-xs: 4px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
  
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-full: 9999px;
  
  --transition: all 0.3s ease;
  
  --category-study: #2196F3;
  --category-exercise: #4CAF50;
  --category-housework: #FF9800;
  --category-habit: #9C27B0;
  --category-other: #607D8B;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html, body {
  height: 100%;
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  color: var(--text-primary);
  background-color: var(--bg-secondary);
  line-height: 1.5;
  -webkit-tap-highlight-color: transparent;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

#app {
  min-height: 100%;
  display: flex;
  flex-direction: column;
}

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

a:active {
  opacity: 0.7;
}

input, button, textarea, select {
  font-family: inherit;
  font-size: inherit;
  outline: none;
}

button {
  cursor: pointer;
  border: none;
  background: none;
}

img {
  max-width: 100%;
  height: auto;
}

ul, ol {
  list-style: none;
}

.hidden {
  display: none !important;
}

.text-center {
  text-align: center;
}

.text-right {
  text-align: right;
}

.text-primary {
  color: var(--primary);
}

.text-danger {
  color: var(--danger);
}

.text-secondary {
  color: var(--text-secondary);
}

.text-success {
  color: var(--success);
}

.mt-sm { margin-top: var(--spacing-sm); }
.mt-md { margin-top: var(--spacing-md); }
.mt-lg { margin-top: var(--spacing-lg); }
.mb-sm { margin-bottom: var(--spacing-sm); }
.mb-md { margin-bottom: var(--spacing-md); }
.mb-lg { margin-bottom: var(--spacing-lg); }

.flex {
  display: flex;
}

.flex-center {
  display: flex;
  align-items: center;
  justify-content: center;
}

.flex-between {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.flex-column {
  flex-direction: column;
}

.flex-1 {
  flex: 1;
}

.loading-screen {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: var(--bg-primary);
  z-index: 9999;
}

.loading-spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--border-color);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.page {
  min-height: 100vh;
  background: var(--bg-secondary);
  padding-bottom: 70px;
}

.page-header {
  background: var(--primary);
  color: var(--text-white);
  padding: var(--spacing-md);
  padding-top: calc(var(--spacing-md) + env(safe-area-inset-top, 0));
}

.page-title {
  font-size: var(--font-size-lg);
  font-weight: 600;
}

.page-content {
  padding: var(--spacing-md);
}

.empty-state {
  text-align: center;
  padding: var(--spacing-xl);
  color: var(--text-secondary);
}

.empty-state-icon {
  font-size: 48px;
  margin-bottom: var(--spacing-md);
}

.empty-state-text {
  font-size: var(--font-size-sm);
}

.skeleton {
  background: linear-gradient(90deg, var(--bg-secondary) 25%, #e0e0e0 50%, var(--bg-secondary) 75%);
  background-size: 200% 100%;
  animation: skeleton-loading 1.5s infinite;
  border-radius: var(--radius-sm);
}

@keyframes skeleton-loading {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}