/**
 * Upflow Brand Colors & Design System
 * ===================================
 * 
 * Brand Color Palette:
 * - Primary (Dark Brown): #3D1A0A
 * - Accent (Red Brown): #8B2500
 * - Background (Cream): #F5F0E8
 */

:root {
  /* Primary Colors */
  --upflow-primary: #3D1A0A;        /* 深褐色 - 主色 */
  --upflow-accent: #8B2500;         /* 红褐色 - 强调色 */
  --upflow-background: #F5F0E8;     /* 米白色 - 背景色 */
  
  /* Extended Palette */
  --upflow-primary-dark: #2D0F06;   /* 更深的褐色 */
  --upflow-primary-light: #5C3A2F;  /* 更浅的褐色 */
  --upflow-accent-dark: #6B1A00;    /* 更深的红褐色 */
  --upflow-accent-light: #A03010;   /* 更浅的红褐色 */
  
  /* Neutral Colors */
  --upflow-white: #FFFFFF;
  --upflow-gray-light: #F9F7F4;     /* 接近背景的浅灰 */
  --upflow-gray-medium: #D4CCC2;    /* 中灰 */
  --upflow-gray-dark: #6B6B6B;      /* 深灰 */
  --upflow-black: #000000;
  
  /* Status Colors */
  --upflow-success: #2E7D32;        /* 成功绿 */
  --upflow-warning: #F57C00;        /* 警告橙 */
  --upflow-error: #C62828;          /* 错误红 */
  --upflow-info: #0277BD;           /* 信息蓝 */
  
  /* Shadows */
  --upflow-shadow-sm: 0 2px 4px rgba(61, 26, 10, 0.1);
  --upflow-shadow-md: 0 4px 8px rgba(61, 26, 10, 0.15);
  --upflow-shadow-lg: 0 8px 16px rgba(61, 26, 10, 0.2);
  
  /* Spacing */
  --upflow-spacing-xs: 4px;
  --upflow-spacing-sm: 8px;
  --upflow-spacing-md: 16px;
  --upflow-spacing-lg: 24px;
  --upflow-spacing-xl: 32px;
  --upflow-spacing-2xl: 48px;
  
  /* Border Radius */
  --upflow-radius-sm: 4px;
  --upflow-radius-md: 8px;
  --upflow-radius-lg: 12px;
  --upflow-radius-xl: 16px;
  
  /* Typography */
  --upflow-font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --upflow-font-size-xs: 12px;
  --upflow-font-size-sm: 14px;
  --upflow-font-size-base: 16px;
  --upflow-font-size-lg: 18px;
  --upflow-font-size-xl: 20px;
  --upflow-font-size-2xl: 24px;
  --upflow-font-size-3xl: 32px;
  
  /* Line Heights */
  --upflow-line-height-tight: 1.2;
  --upflow-line-height-normal: 1.5;
  --upflow-line-height-relaxed: 1.75;
}

/* ============================================================================
 * Global Styles
 * ============================================================================ */

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

html {
  font-family: var(--upflow-font-family);
  font-size: 16px;
  line-height: var(--upflow-line-height-normal);
  color: var(--upflow-gray-dark);
  background-color: var(--upflow-background);
}

body {
  background-color: var(--upflow-background);
  color: var(--upflow-gray-dark);
  min-height: 100vh;
}

/* ============================================================================
 * Typography
 * ============================================================================ */

h1, h2, h3, h4, h5, h6 {
  color: var(--upflow-primary);
  font-weight: 700;
  line-height: var(--upflow-line-height-tight);
  margin-bottom: var(--upflow-spacing-md);
}

h1 {
  font-size: var(--upflow-font-size-3xl);
}

h2 {
  font-size: var(--upflow-font-size-2xl);
}

h3 {
  font-size: var(--upflow-font-size-xl);
}

h4 {
  font-size: var(--upflow-font-size-lg);
}

h5, h6 {
  font-size: var(--upflow-font-size-base);
}

p {
  margin-bottom: var(--upflow-spacing-md);
  line-height: var(--upflow-line-height-relaxed);
}

a {
  color: var(--upflow-accent);
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  color: var(--upflow-accent-dark);
  text-decoration: underline;
}

/* ============================================================================
 * Navigation & Header
 * ============================================================================ */

nav, header {
  background-color: var(--upflow-primary);
  color: var(--upflow-white);
  padding: var(--upflow-spacing-lg);
  box-shadow: var(--upflow-shadow-md);
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--upflow-spacing-lg);
}

.logo {
  font-size: var(--upflow-font-size-2xl);
  font-weight: 700;
  color: var(--upflow-white);
  display: flex;
  align-items: center;
  gap: var(--upflow-spacing-sm);
}

.nav-items {
  display: flex;
  gap: var(--upflow-spacing-lg);
  flex-wrap: wrap;
}

.nav-items a {
  color: var(--upflow-white);
  padding: var(--upflow-spacing-sm) var(--upflow-spacing-md);
  border-radius: var(--upflow-radius-md);
  transition: background-color 0.2s ease;
}

.nav-items a:hover {
  background-color: var(--upflow-accent);
  text-decoration: none;
}

/* ============================================================================
 * Buttons
 * ============================================================================ */

button, .btn {
  font-family: var(--upflow-font-family);
  font-size: var(--upflow-font-size-base);
  padding: var(--upflow-spacing-sm) var(--upflow-spacing-lg);
  border: none;
  border-radius: var(--upflow-radius-md);
  cursor: pointer;
  transition: all 0.2s ease;
  font-weight: 600;
  text-align: center;
  display: inline-block;
}

/* Primary Button - Red Brown */
.btn-primary, button.btn-primary {
  background-color: var(--upflow-accent);
  color: var(--upflow-white);
  box-shadow: var(--upflow-shadow-sm);
}

.btn-primary:hover, button.btn-primary:hover {
  background-color: var(--upflow-accent-dark);
  transform: translateY(-2px);
  box-shadow: var(--upflow-shadow-md);
}

.btn-primary:active, button.btn-primary:active {
  transform: translateY(0);
}

/* Secondary Button - Primary */
.btn-secondary, button.btn-secondary {
  background-color: var(--upflow-primary);
  color: var(--upflow-white);
  box-shadow: var(--upflow-shadow-sm);
}

.btn-secondary:hover, button.btn-secondary:hover {
  background-color: var(--upflow-primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--upflow-shadow-md);
}

/* Outline Button */
.btn-outline, button.btn-outline {
  background-color: transparent;
  color: var(--upflow-accent);
  border: 2px solid var(--upflow-accent);
}

.btn-outline:hover, button.btn-outline:hover {
  background-color: var(--upflow-accent);
  color: var(--upflow-white);
}

/* Ghost Button */
.btn-ghost, button.btn-ghost {
  background-color: transparent;
  color: var(--upflow-primary);
  border: 1px solid var(--upflow-primary);
}

.btn-ghost:hover, button.btn-ghost:hover {
  background-color: var(--upflow-primary);
  color: var(--upflow-white);
}

/* Disabled Button */
button:disabled, .btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none !important;
}

/* Button Sizes */
.btn-sm {
  padding: var(--upflow-spacing-xs) var(--upflow-spacing-md);
  font-size: var(--upflow-font-size-sm);
}

.btn-lg {
  padding: var(--upflow-spacing-md) var(--upflow-spacing-xl);
  font-size: var(--upflow-font-size-lg);
}

/* ============================================================================
 * Cards & Containers
 * ============================================================================ */

.card, .container {
  background-color: var(--upflow-white);
  border-radius: var(--upflow-radius-lg);
  padding: var(--upflow-spacing-lg);
  box-shadow: var(--upflow-shadow-sm);
  transition: box-shadow 0.2s ease;
  border-left: 4px solid var(--upflow-primary);
}

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

.card-header {
  border-bottom: 2px solid var(--upflow-background);
  padding-bottom: var(--upflow-spacing-md);
  margin-bottom: var(--upflow-spacing-md);
}

.card-header h3 {
  margin: 0;
  color: var(--upflow-primary);
}

.card-body {
  padding: var(--upflow-spacing-md) 0;
}

.card-footer {
  border-top: 1px solid var(--upflow-background);
  padding-top: var(--upflow-spacing-md);
  margin-top: var(--upflow-spacing-md);
}

/* ============================================================================
 * Forms
 * ============================================================================ */

input, textarea, select {
  font-family: var(--upflow-font-family);
  font-size: var(--upflow-font-size-base);
  padding: var(--upflow-spacing-sm) var(--upflow-spacing-md);
  border: 1px solid var(--upflow-gray-medium);
  border-radius: var(--upflow-radius-md);
  color: var(--upflow-gray-dark);
  background-color: var(--upflow-white);
  transition: border-color 0.2s ease;
}

input:focus, textarea:focus, select:focus {
  outline: none;
  border-color: var(--upflow-accent);
  box-shadow: 0 0 0 3px rgba(139, 37, 0, 0.1);
}

input::placeholder {
  color: var(--upflow-gray-medium);
}

label {
  display: block;
  margin-bottom: var(--upflow-spacing-sm);
  color: var(--upflow-primary);
  font-weight: 600;
}

.form-group {
  margin-bottom: var(--upflow-spacing-lg);
}

.form-error {
  color: var(--upflow-error);
  font-size: var(--upflow-font-size-sm);
  margin-top: var(--upflow-spacing-xs);
}

.form-help {
  color: var(--upflow-gray-medium);
  font-size: var(--upflow-font-size-sm);
  margin-top: var(--upflow-spacing-xs);
}

/* ============================================================================
 * Alerts & Notifications
 * ============================================================================ */

.alert {
  padding: var(--upflow-spacing-md);
  border-radius: var(--upflow-radius-md);
  margin-bottom: var(--upflow-spacing-md);
  border-left: 4px solid;
}

.alert-success {
  background-color: rgba(46, 125, 50, 0.1);
  color: var(--upflow-success);
  border-color: var(--upflow-success);
}

.alert-warning {
  background-color: rgba(245, 124, 0, 0.1);
  color: var(--upflow-warning);
  border-color: var(--upflow-warning);
}

.alert-error {
  background-color: rgba(198, 40, 40, 0.1);
  color: var(--upflow-error);
  border-color: var(--upflow-error);
}

.alert-info {
  background-color: rgba(2, 119, 189, 0.1);
  color: var(--upflow-info);
  border-color: var(--upflow-info);
}

/* ============================================================================
 * Progress & Loading
 * ============================================================================ */

.progress {
  height: 8px;
  background-color: var(--upflow-background);
  border-radius: var(--upflow-radius-lg);
  overflow: hidden;
  margin-bottom: var(--upflow-spacing-md);
}

.progress-bar {
  height: 100%;
  background-color: var(--upflow-accent);
  transition: width 0.3s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--upflow-white);
  font-size: var(--upflow-font-size-xs);
  font-weight: 600;
}

/* Spinner */
.spinner {
  border: 3px solid var(--upflow-background);
  border-top-color: var(--upflow-accent);
  border-radius: 50%;
  width: 40px;
  height: 40px;
  animation: spin 1s linear infinite;
  margin: auto;
}

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

/* ============================================================================
 * Utilities
 * ============================================================================ */

.text-primary { color: var(--upflow-primary); }
.text-accent { color: var(--upflow-accent); }
.text-success { color: var(--upflow-success); }
.text-warning { color: var(--upflow-warning); }
.text-error { color: var(--upflow-error); }
.text-light { color: var(--upflow-gray-medium); }

.bg-primary { background-color: var(--upflow-primary); }
.bg-accent { background-color: var(--upflow-accent); }
.bg-light { background-color: var(--upflow-background); }

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

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

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

.p-sm { padding: var(--upflow-spacing-sm); }
.p-md { padding: var(--upflow-spacing-md); }
.p-lg { padding: var(--upflow-spacing-lg); }

.rounded { border-radius: var(--upflow-radius-md); }
.rounded-lg { border-radius: var(--upflow-radius-lg); }

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

/* ============================================================================
 * Responsive Design
 * ============================================================================ */

@media (max-width: 768px) {
  nav {
    flex-direction: column;
    align-items: flex-start;
  }
  
  .nav-items {
    width: 100%;
    flex-direction: column;
  }
  
  h1 {
    font-size: var(--upflow-font-size-2xl);
  }
  
  h2 {
    font-size: var(--upflow-font-size-xl);
  }
  
  .card, .container {
    padding: var(--upflow-spacing-md);
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: var(--upflow-font-size-xl);
  }
  
  .btn {
    width: 100%;
  }
  
  input, textarea, select {
    width: 100%;
  }
}