/* HSK 5 Study Website - Main Stylesheet */
/* Author: AI Assistant */
/* Date: June 2025 */

/* Import flashcard and quiz specific styles */
@import url('flashcard-styles.css');

/* ===== GLOBAL STYLES ===== */
:root {
  /* Color Scheme */
  --primary-color: #3498db;       /* Blue - primary brand color */
  --secondary-color: #e74c3c;     /* Red - accent color */
  --tertiary-color: #f1c40f;      /* Yellow - highlight color */
  --dark-color: #2c3e50;          /* Dark blue/gray - text and headers */
  --light-color: #ecf0f1;         /* Light gray - backgrounds */
  --white-color: #ffffff;         /* White - card backgrounds */
  --success-color: #2ecc71;       /* Green - success messages */
  --danger-color: #e74c3c;        /* Red - error messages */
  --info-color: #3498db;          /* Blue - info messages */
  --warning-color: #f39c12;       /* Orange - warning messages */
  --text-color: #333333;          /* Dark gray - main text */
  --text-light-color: #7f8c8d;    /* Medium gray - secondary text */
  --border-color: #dcdde1;        /* Light gray - borders */
  --primary-light-color: #ebf5fb; /* Light blue - backgrounds */
  
  /* Typography */
  --body-font: 'Noto Sans', 'Noto Sans SC', sans-serif;
  --heading-font: 'Noto Serif', 'Noto Serif SC', serif;
  
  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2.5rem;
  
  /* Border Radius */
  --border-radius: 8px;
  
  /* Transitions */
  --transition-speed: 0.3s;
}

/* Reset and Base Styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

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

body {
  font-family: var(--body-font);
  line-height: 1.6;
  color: var(--dark-color);
  background-color: var(--light-color);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--heading-font);
  margin-bottom: var(--spacing-md);
  color: var(--dark-color);
  line-height: 1.2;
}

h1 {
  font-size: 2.5rem;
}

h2 {
  font-size: 2rem;
}

h3 {
  font-size: 1.75rem;
}

h4 {
  font-size: 1.5rem;
}

h5 {
  font-size: 1.25rem;
}

h6 {
  font-size: 1rem;
}

p {
  margin-bottom: var(--spacing-md);
}

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

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

/* Chinese Text Styling */
.chinese {
  font-family: 'Noto Sans SC', sans-serif;
}

.pinyin {
  font-style: italic;
  color: var(--dark-color);
  opacity: 0.8;
}

/* ===== LAYOUT ===== */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

.section {
  padding: var(--spacing-xl) 0;
}

.section-title {
  text-align: center;
  margin-bottom: var(--spacing-xl);
}

.section-subtitle {
  text-align: center;
  font-size: 1.2rem;
  margin-top: -1rem;
  margin-bottom: var(--spacing-lg);
  color: var(--dark-color);
  opacity: 0.8;
}

/* Grid System */
.row {
  display: flex;
  flex-wrap: wrap;
  margin: 0 -15px;
}

.col {
  padding: 0 15px;
  flex: 1;
}

/* For different column sizes */
.col-1 { flex: 0 0 8.33%; max-width: 8.33%; }
.col-2 { flex: 0 0 16.66%; max-width: 16.66%; }
.col-3 { flex: 0 0 25%; max-width: 25%; }
.col-4 { flex: 0 0 33.33%; max-width: 33.33%; }
.col-5 { flex: 0 0 41.66%; max-width: 41.66%; }
.col-6 { flex: 0 0 50%; max-width: 50%; }
.col-7 { flex: 0 0 58.33%; max-width: 58.33%; }
.col-8 { flex: 0 0 66.66%; max-width: 66.66%; }
.col-9 { flex: 0 0 75%; max-width: 75%; }
.col-10 { flex: 0 0 83.33%; max-width: 83.33%; }
.col-11 { flex: 0 0 91.66%; max-width: 91.66%; }
.col-12 { flex: 0 0 100%; max-width: 100%; }

/* ===== HEADER & NAVIGATION ===== */
.header {
  background-color: var(--white-color);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
  position: sticky;
  top: 0;
  z-index: 1000;
}

.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-md) 0;
}

.logo {
  display: flex;
  align-items: center;
}

.logo img {
  height: 40px;
  margin-right: var(--spacing-sm);
}

.logo-text {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--primary-color);
}

.nav-menu {
  display: flex;
  list-style: none;
}

.nav-item {
  margin-left: var(--spacing-lg);
}

.nav-link {
  font-weight: 500;
  position: relative;
  padding-bottom: 5px;
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--secondary-color);
  transition: width var(--transition-speed);
}

.nav-link:hover::after,
.nav-link.active::after {
  width: 100%;
}

.hamburger {
  display: none;
  cursor: pointer;
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--dark-color);
}

/* ===== HERO SECTION ===== */
.hero {
  background: linear-gradient(135deg, var(--primary-color), var(--dark-color));
  color: var(--white-color);
  text-align: center;
  padding: var(--spacing-xl) 0;
}

.hero-content {
  max-width: 800px;
  margin: 0 auto;
}

.hero-title {
  font-size: 3rem;
  margin-bottom: var(--spacing-md);
  color: var(--white-color);
}

.hero-subtitle {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-lg);
  opacity: 0.9;
}

/* ===== BUTTONS ===== */
.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  border-radius: var(--border-radius);
  font-weight: 600;
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-speed);
  border: none;
}

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

.btn-primary:hover {
  background-color: #2980b9;
  color: var(--white-color);
}

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

.btn-secondary:hover {
  background-color: #c0392b;
  color: var(--white-color);
}

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

.btn-success:hover {
  background-color: #27ae60;
  color: var(--white-color);
}

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

.btn-warning:hover {
  background-color: #e67e22;
  color: var(--white-color);
}

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

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

.btn-lg {
  padding: 1rem 2rem;
  font-size: 1.1rem;
}

.btn-sm {
  padding: 0.5rem 1rem;
  font-size: 0.9rem;
}

/* ===== CARDS ===== */
.card {
  background-color: var(--white-color);
  border-radius: var(--border-radius);
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
  transition: transform var(--transition-speed), box-shadow var(--transition-speed);
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
}

.card-title {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-md);
}

.card-icon {
  font-size: 2.5rem;
  color: var(--primary-color);
  margin-bottom: var(--spacing-md);
}

/* ===== FEATURES SECTION ===== */
.features {
  text-align: center;
}

.feature-card {
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
}

/* ===== PROGRESS BAR ===== */
.progress {
  height: 10px;
  background-color: var(--light-color);
  border-radius: 5px;
  overflow: hidden;
  margin-bottom: var(--spacing-sm);
}

.progress-bar {
  height: 100%;
  background-color: var(--primary-color);
  border-radius: 5px;
  transition: width 0.3s ease;
}

/* ===== FORM ELEMENTS ===== */
.form-control {
  display: block;
  width: 100%;
  padding: 0.75rem;
  font-size: 1rem;
  line-height: 1.5;
  color: var(--dark-color);
  background-color: var(--white-color);
  background-clip: padding-box;
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  transition: border-color var(--transition-speed);
}

.form-control:focus {
  border-color: var(--primary-color);
  outline: 0;
  box-shadow: 0 0 0 0.2rem rgba(52, 152, 219, 0.25);
}

.checkbox-group {
  margin-bottom: var(--spacing-sm);
}

.checkbox-group label {
  display: flex;
  align-items: center;
  cursor: pointer;
}

.checkbox-group input[type="checkbox"] {
  margin-right: var(--spacing-sm);
}

/* ===== STUDY PLAN ===== */
.timeline {
  position: relative;
  max-width: 1200px;
  margin: 0 auto;
}

.timeline::after {
  content: '';
  position: absolute;
  width: 6px;
  background-color: var(--light-color);
  top: 0;
  bottom: 0;
  left: 50%;
  margin-left: -3px;
}

.timeline-item {
  padding: 10px 40px;
  position: relative;
  width: 50%;
}

.timeline-item::after {
  content: '';
  position: absolute;
  width: 25px;
  height: 25px;
  right: -12px;
  background-color: var(--white-color);
  border: 4px solid var(--primary-color);
  top: 15px;
  border-radius: 50%;
  z-index: 1;
}

.timeline-item.left {
  left: 0;
}

.timeline-item.right {
  left: 50%;
}

.timeline-item.right::after {
  left: -12px;
}

.timeline-content {
  padding: var(--spacing-md);
  background-color: var(--white-color);
  position: relative;
  border-radius: var(--border-radius);
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

/* ===== FOOTER ===== */
.footer {
  background-color: var(--dark-color);
  color: var(--white-color);
  padding: var(--spacing-xl) 0;
}

.footer-content {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
}

.footer-section {
  flex: 1;
  min-width: 200px;
  margin-bottom: var(--spacing-lg);
}

.footer-title {
  color: var(--white-color);
  margin-bottom: var(--spacing-md);
  font-size: 1.2rem;
}

.footer-links {
  list-style: none;
}

.footer-link {
  margin-bottom: var(--spacing-sm);
}

.footer-link a {
  color: var(--light-color);
  transition: color var(--transition-speed);
}

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

.footer-bottom {
  text-align: center;
  padding-top: var(--spacing-lg);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  margin-top: var(--spacing-lg);
}

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

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

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

.mb-1 {
  margin-bottom: var(--spacing-xs);
}

.mb-2 {
  margin-bottom: var(--spacing-sm);
}

.mb-3 {
  margin-bottom: var(--spacing-md);
}

.mb-4 {
  margin-bottom: var(--spacing-lg);
}

.mb-5 {
  margin-bottom: var(--spacing-xl);
}

.mt-1 {
  margin-top: var(--spacing-xs);
}

.mt-2 {
  margin-top: var(--spacing-sm);
}

.mt-3 {
  margin-top: var(--spacing-md);
}

.mt-4 {
  margin-top: var(--spacing-lg);
}

.mt-5 {
  margin-top: var(--spacing-xl);
}

/* ===== RESPONSIVE DESIGN ===== */
@media (max-width: 992px) {
  html {
    font-size: 15px;
  }
  
  .timeline::after {
    left: 31px;
  }
  
  .timeline-item {
    width: 100%;
    padding-left: 70px;
    padding-right: 25px;
  }
  
  .timeline-item.right {
    left: 0;
  }
  
  .timeline-item::after {
    left: 18px;
  }
  
  .timeline-item.right::after {
    left: 18px;
  }
  
  .offset-lg-1 {
    margin-left: 0;
  }
  
  .col-lg-10 {
    flex: 0 0 100%;
    max-width: 100%;
  }
  
  .col-lg-4 {
    flex: 0 0 50%;
    max-width: 50%;
  }
}

@media (max-width: 768px) {
  html {
    font-size: 14px;
  }
  
  .nav-menu {
    position: fixed;
    top: 70px;
    left: -100%;
    flex-direction: column;
    background-color: var(--white-color);
    width: 100%;
    text-align: center;
    transition: 0.3s;
    box-shadow: 0 10px 10px rgba(0, 0, 0, 0.1);
    padding: var(--spacing-md) 0;
  }
  
  .nav-menu.active {
    left: 0;
  }
  
  .nav-item {
    margin: var(--spacing-sm) 0;
  }
  
  .hamburger {
    display: block;
  }
  
  .col-md-6 {
    flex: 0 0 50%;
    max-width: 50%;
  }
  
  .col-md-12 {
    flex: 0 0 100%;
    max-width: 100%;
  }
  
  .col-lg-4 {
    flex: 0 0 100%;
    max-width: 100%;
  }
}

@media (max-width: 576px) {
  .hero-title {
    font-size: 2.5rem;
  }
  
  .hero-subtitle {
    font-size: 1.2rem;
  }
  
  .col-sm-12 {
    flex: 0 0 100%;
    max-width: 100%;
  }
  
  .footer-content {
    flex-direction: column;
  }
  
  .btn-group {
    flex-direction: column;
  }
  
  .btn-group .btn {
    margin-bottom: var(--spacing-sm);
  }
}