:root {
    --font-main: 'Kanit', sans-serif;
 
    --dk-deep-blue: #0D1E4C;
    --dk-muted-blue: #26415E;
    --dk-darkest-blue: #0B1632;
    --lt-dusty-rose: #C48CB3; 
    --lt-pale-pink: #E6C9D7; 
    --lt-sky-blue: #83A6CE; 
  
    --bg-color: var(--dk-darkest-blue); 
    --text-color: var(--lt-pale-pink); 
    --heading-color: #ffffff; 
    --primary-color: var(--lt-dusty-rose); 
    --primary-hover: #d1a0c0; 
    --secondary-color: var(--lt-sky-blue); 
    --card-bg: var(--dk-muted-blue); 
    --card-border: #3a5a7a; 
    --header-bg: var(--dk-deep-blue); 
    --link-color: var(--primary-color);
    --link-hover: var(--primary-hover);
    --icon-color: var(--secondary-color); 
    --border-color: var(--primary-color); 
    --shadow-color: rgba(0, 0, 0, 0.4);
    --status-teaching-bg: rgba(131, 166, 206, 0.2); 
    --status-teaching-text: var(--lt-sky-blue);
    --status-completed-bg: rgba(196, 140, 179, 0.2); 
    --status-completed-text: var(--lt-dusty-rose);

    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-xxl: 3rem;
  
    --transition-speed: 0.3s;
    --transition-speed-fast: 0.2s;
  }
  
  body.light-theme {
   
    --lt-bg: #f8faff; 
    --lt-text: #26415E; 
    --lt-heading: #0D1E4C; 
    --lt-primary: #a35f9e; 
    --lt-primary-hover: #8e4a86;
    --lt-secondary: #5a87b8; 
    --lt-card-bg: #ffffff; 
    --lt-card-border: #e8eef3; 
    --lt-header-bg: #ffffff;
    --lt-link: var(--lt-primary);
    --lt-link-hover: var(--lt-primary-hover);
    --lt-icon: var(--lt-secondary);
    --lt-border: var(--lt-primary);
    --lt-shadow: rgba(13, 30, 76, 0.1); 

    --bg-color: var(--lt-bg);
    --text-color: var(--lt-text);
    --heading-color: var(--lt-heading);
    --primary-color: var(--lt-primary);
    --primary-hover: var(--lt-primary-hover);
    --secondary-color: var(--lt-secondary);
    --card-bg: var(--lt-card-bg);
    --card-border: var(--lt-card-border);
    --header-bg: var(--lt-header-bg);
    --link-color: var(--lt-link);
    --link-hover: var(--lt-link-hover);
    --icon-color: var(--lt-icon);
    --border-color: var(--lt-border);
    --shadow-color: var(--lt-shadow);

    --status-teaching-bg: rgba(90, 135, 184, 0.15);
    --status-teaching-text: var(--lt-secondary);
    --status-completed-bg: rgba(163, 95, 158, 0.15);
    --status-completed-text: var(--lt-primary);
  }

  *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
  html { scroll-behavior: smooth; font-size: 16px; }
  body {
    font-family: var(--font-main);
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.7;
    transition: background-color var(--transition-speed) ease, color var(--transition-speed) ease;
    overflow-x: hidden;
  }

  .container { max-width: 1140px; margin: 0 auto; padding: 0 var(--spacing-lg); }
  
  .site-header {
    background-color: var(--header-bg);
    padding: var(--spacing-sm) 0;
    position: sticky; top: 0; z-index: 1000;
    box-shadow: 0 3px 15px var(--shadow-color); 
    transition: background-color var(--transition-speed) ease;
  }
  .header-container { display: flex; justify-content: space-between; align-items: center; }
  .logo h1 { font-size: 1.6rem; font-weight: 700; color: var(--heading-color); margin: 0; transition: color var(--transition-speed) ease; }
  a.logo { text-decoration: none; }
  a.logo:hover h1 { color: var(--primary-color); }
  
  .main-nav a {
    color: var(--text-color);
    margin-left: var(--spacing-lg);
    text-decoration: none; font-weight: 500;
    transition: color var(--transition-speed-fast) ease;
    position: relative; padding-bottom: var(--spacing-xs);
  }
  .main-nav a:hover, .main-nav a:focus, .main-nav a.active { 
    color: var(--primary-color);
  }
  .main-nav a::after {
      content: ''; position: absolute; bottom: -2px; 
      left: 0; width: 0; height: 2px;
      background-color: var(--primary-color);
      transition: width var(--transition-speed-fast) ease;
  }
  .main-nav a:hover::after, .main-nav a:focus::after, .main-nav a.active::after {
      width: 100%;
  }
  .header-controls { display: flex; align-items: center; gap: var(--spacing-md); }
  
  .toggle-theme label {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 30px; cursor: pointer; display: flex;
    justify-content: space-between; align-items: center;
    position: relative; height: 26px; width: 50px; padding: 4px;
    transition: background-color var(--transition-speed) ease, border-color var(--transition-speed) ease;
  }
  .toggle-theme .moon-icon, .toggle-theme .sun-icon {
    font-size: 0.8rem; color: var(--secondary-color);
    z-index: 1; transition: color var(--transition-speed) ease, opacity var(--transition-speed) ease;
  }
  .toggle-theme .ball {
    background: var(--secondary-color); 
    border-radius: 50%; position: absolute; top: 2px; left: 2px;
    height: 20px; width: 20px;
    transition: transform var(--transition-speed) ease, background-color var(--transition-speed) ease;
  }
  #theme-toggle { display: none; }
  #theme-toggle:checked + label .ball { transform: translateX(24px); }
  #theme-toggle:checked + label .moon-icon { opacity: 0; }
  #theme-toggle:not(:checked) + label .sun-icon { opacity: 0; }
  #theme-toggle:checked + label .sun-icon { opacity: 1; }
  
  .mobile-menu-toggle { display: none; background: none; border: none; color: var(--text-color); font-size: 1.5rem; cursor: pointer; padding: var(--spacing-sm); }
  .mobile-nav { display: none; background-color: var(--header-bg); position: absolute; top: 100%; left: 0; width: 100%; padding: var(--spacing-md) 0; box-shadow: 0 5px 10px var(--shadow-color); border-top: 1px solid var(--card-border); z-index: 999; }
  .mobile-nav.active { display: block; }
  .mobile-nav-link { display: block; color: var(--text-color); text-decoration: none; padding: var(--spacing-md) var(--spacing-lg); text-align: center; transition: background-color var(--transition-speed) ease, color var(--transition-speed) ease; }
  .mobile-nav-link:hover, .mobile-nav-link:focus { background-color: var(--card-bg); color: var(--primary-color); }
  
  .btn {
      display: inline-block;
      padding: var(--spacing-sm) var(--spacing-lg);
      border-radius: 5px;
      text-decoration: none;
      font-weight: 500;
      cursor: pointer;
      transition: background-color var(--transition-speed-fast) ease, transform var(--transition-speed-fast) ease, box-shadow var(--transition-speed-fast) ease;
      border: none;
      font-family: var(--font-main);
      font-size: 1rem;
  }
  
  .btn-primary {
      background-color: var(--primary-color);
      color: var(--dk-darkest-blue); 
      box-shadow: 0 2px 5px rgba(0,0,0,0.2);
  }
  body.light-theme .btn-primary {
       color: #fff;
  }
  
  .btn-primary:hover, .btn-primary:focus {
      background-color: var(--primary-hover);
      transform: translateY(-2px);
      box-shadow: 0 4px 8px rgba(0,0,0,0.3);
  }
  
  .hero-slider { margin-bottom: var(--spacing-xxl); position: relative; } 
  .swiper { width: 100%; aspect-ratio: 16 / 7; max-height: 65vh; }
  .swiper-slide { text-align: center; font-size: 18px; background: var(--dk-muted-blue); display: flex; justify-content: center; align-items: center; position: relative; overflow: hidden; } /* Relative for overlay */
  .swiper-slide img { display: block; width: 100%; height: 100%; object-fit: cover; transition: transform 0.6s ease; } 
  .swiper-slide:hover img { transform: scale(1.05); } 
  
  .slide-content {
      position: absolute;
      bottom: 10%; 
      left: 5%;
      max-width: 50%; 
      background-color: rgba(11, 22, 50, 0.7); 
      color: #fff;
      padding: var(--spacing-lg);
      border-radius: 8px;
      text-align: left;
      z-index: 10;
  }
  .slide-content h2 {
      font-size: 2rem;
      margin-bottom: var(--spacing-sm);
      color: #fff; 
  }
  .slide-content p {
      font-size: 1rem;
      margin-bottom: var(--spacing-md);
      color: var(--lt-pale-pink); 
  }
  
  .swiper-pagination-bullet { background: rgba(255, 255, 255, 0.6); opacity: 1; transition: background-color var(--transition-speed-fast) ease; }
  .swiper-pagination-bullet-active { background: var(--primary-color); }
  .swiper-button-prev, .swiper-button-next {
      color: #fff; 
      background-color: rgba(13, 30, 76, 0.4); 
      border-radius: 50%; width: 44px; height: 44px;
      transition: background-color var(--transition-speed) ease, color var(--transition-speed) ease;
  }
  .swiper-button-prev:hover, .swiper-button-next:hover { background-color: rgba(13, 30, 76, 0.7); color: var(--primary-color); }
  .swiper-button-prev::after, .swiper-button-next::after { font-size: 1.3rem; font-weight: bold; }
  
  .content-section { padding: var(--spacing-xxl) 0; border-bottom: 1px solid var(--card-border); }
  .content-section:last-of-type { border-bottom: none; }
  .content-section h2 {
      color: var(--heading-color); font-size: 2.2rem; font-weight: 700;
      margin-bottom: var(--spacing-xl); padding-bottom: var(--spacing-sm);
      border-bottom: 4px solid var(--primary-color); 
      display: inline-block;
  }
  
  .overview-section {
      background-color: rgba(var(--dk-muted-blue), 0.3); 
      border-radius: 10px;
      padding: var(--spacing-xl); 
      margin-bottom: var(--spacing-xxl); 
  }
  body.light-theme .overview-section {
      background-color: rgba(var(--lt-secondary), 0.08);
  }
  
  .overview-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
      gap: var(--spacing-lg);
      text-align: center;
  }
  
  .overview-card {
      background-color: var(--card-bg);
      padding: var(--spacing-lg);
      border-radius: 8px;
      border: 1px solid var(--card-border);
      box-shadow: 0 2px 8px var(--shadow-color);
      transition: transform var(--transition-speed) ease, box-shadow var(--transition-speed) ease;
  }
  
  .overview-card:hover {
      transform: translateY(-6px) scale(1.03); 
      box-shadow: 0 6px 15px var(--shadow-color);
  }
  
  .overview-card .icon-large {
      font-size: 2.5rem;
      color: var(--primary-color); 
      margin-bottom: var(--spacing-md);
      display: block; 
  }
  
  .overview-number {
      display: block;
      font-size: 2rem;
      font-weight: 700;
      color: var(--heading-color);
      margin-bottom: var(--spacing-xs);
  }
  
  .overview-label {
      font-size: 0.9rem;
      color: var(--text-color);
      opacity: 0.8;
  }
  
  .course-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: var(--spacing-lg); }
  .course-card {
      background-color: var(--card-bg); padding: var(--spacing-lg);
      border-radius: 10px; border: 1px solid var(--card-border);
      box-shadow: 0 4px 15px var(--shadow-color);
      transition: transform var(--transition-speed) ease, box-shadow var(--transition-speed) ease;
      display: flex; flex-direction: column; overflow: hidden; 
  }
  .course-card:hover { transform: translateY(-8px); box-shadow: 0 10px 25px var(--shadow-color); }
  .course-icon { font-size: 2.2rem; color: var(--secondary-color); margin-bottom: var(--spacing-md); align-self: flex-start; }
  .course-card h3 { color: var(--heading-color); margin: 0 0 var(--spacing-sm) 0; font-size: 1.5rem; font-weight: 500; }
  .course-status { display: inline-block; padding: var(--spacing-xs) var(--spacing-md); border-radius: 5px; font-size: 0.8rem; font-weight: 500; margin-bottom: var(--spacing-md); align-self: flex-start; }
  .course-status.teaching { background-color: var(--status-teaching-bg); color: var(--status-teaching-text); }
  .course-status.completed { background-color: var(--status-completed-bg); color: var(--status-completed-text); }
  .course-card p { margin-bottom: var(--spacing-md); flex-grow: 1; opacity: 0.9; }
  .course-link { color: var(--link-color); text-decoration: none; font-weight: 500; align-self: flex-end; margin-top: auto; transition: color var(--transition-speed) ease; padding: var(--spacing-xs) 0; /* Add padding for easier clicking */}
  .course-link:hover, .course-link:focus { color: var(--link-hover); text-decoration: none; } /* Remove underline, rely on color change */
  .course-link i { margin-left: var(--spacing-xs); transition: transform var(--transition-speed-fast) ease; }
  .course-link:hover i { transform: translateX(5px); }
  
  .resource-columns { display: grid; grid-template-columns: 1fr; gap: var(--spacing-xl); }
  @media (min-width: 768px) { .resource-columns { grid-template-columns: repeat(2, 1fr); } }
  .resource-category h3 { color: var(--heading-color); font-size: 1.6rem; margin-bottom: var(--spacing-md); font-weight: 500; display: flex; align-items: center; gap: var(--spacing-sm); }
  .icon-prefix { color: var(--icon-color); }
  .resource-list { list-style: none; padding-left: 0; }
  .resource-list li { margin-bottom: var(--spacing-sm); }
  .resource-list a { color: var(--link-color); text-decoration: none; display: inline-flex; align-items: center; gap: var(--spacing-sm); transition: color var(--transition-speed) ease, letter-spacing var(--transition-speed) ease; }
  .resource-list a:hover, .resource-list a:focus { color: var(--link-hover); letter-spacing: 0.5px; /* Subtle letter spacing on hover */ }
  .resource-list a i { color: var(--icon-color); width: 1.2em; text-align: center; }
  
  .contact-info { font-size: 1.1rem; } 
  .contact-info p { margin-bottom: var(--spacing-md); display: flex; align-items: center; gap: var(--spacing-sm); }
  .contact-info i { color: var(--icon-color); font-size: 1.3rem; width: 1.6em; text-align: center; }
  .contact-info a { color: var(--link-color); text-decoration: none; transition: color var(--transition-speed) ease; }
  .contact-info a:hover, .contact-info a:focus { color: var(--link-hover); text-decoration: underline; }
  
  .site-footer { text-align: center; background: var(--header-bg); color: var(--text-color); padding: var(--spacing-xl) 0; margin-top: var(--spacing-xxl); font-size: 0.9rem; opacity: 0.9; transition: background-color var(--transition-speed) ease, color var(--transition-speed) ease; }
  .site-footer p { margin-bottom: var(--spacing-xs); }
  
  @media (max-width: 992px) {
      html { font-size: 15px; }
      .container { padding: 0 var(--spacing-md); }
      .content-section h2 { font-size: 2rem; }
      .course-card h3 { font-size: 1.4rem; }
      .slide-content { max-width: 65%; }
      .slide-content h2 { font-size: 1.8rem;}
  }
  
  @media (max-width: 767px) {
      html { font-size: 14px; }
      .main-nav { display: none; }
      .mobile-menu-toggle { display: block; }
      .header-container { padding: 0 var(--spacing-md); }
      .logo h1 { font-size: 1.4rem; }
      .swiper { aspect-ratio: 16 / 9; }
      .swiper-button-prev, .swiper-button-next { display: none; }
      .slide-content { max-width: 80%; left: 50%; transform: translateX(-50%); bottom: 5%; padding: var(--spacing-md); text-align: center; }
      .slide-content h2 { font-size: 1.5rem; }
      .slide-content p { font-size: 0.9rem; margin-bottom: var(--spacing-sm); }
      .btn { padding: var(--spacing-sm) var(--spacing-md); font-size: 0.9rem; }
      .content-section { padding: var(--spacing-xl) 0; }
      .content-section h2 { font-size: 1.8rem; }
      .overview-grid { grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: var(--spacing-md); } 
      .overview-card .icon-large { font-size: 2rem; }
      .overview-number { font-size: 1.6rem; }
  }
  
  [data-aos="fade-in"] {
      opacity: 0;
      transition-property: opacity;
  }
  [data-aos="fade-in"].aos-animate {
      opacity: 1;
  }
  
  [data-aos="fade-up"] {
      transform: translateY(30px);
      opacity: 0;
      transition-property: transform, opacity;
  }
  [data-aos="fade-up"].aos-animate {
      transform: translateY(0);
      opacity: 1;
  }