:root {
   --c-blue-primary: #004e92;
   --c-blue-secondary: #00c6ff;
   --c-gradient-main: linear-gradient(135deg, var(--c-blue-primary) 0%, var(--c-blue-secondary) 100%);
   --c-bg: #f4f7f6;
   --c-bg-content: #ffffff;
   --c-bg-content-area: #f9f9fb;
   --c-bg-tab: #ffffff;
   --c-bg-tab-active: var(--c-gradient-main);
   --c-bg-tab-hover: rgba(0, 78, 146, 0.1);
   --c-bg-scroll-top: var(--c-gradient-main);
   --c-text-primary: #1a1a1a;
   --c-text-secondary: #333333;
   --c-text-muted: #6c757d;
   --c-text-tab: #495057;
   --c-text-tab-hover: var(--c-blue-primary);
   --c-text-tab-active: white;
   --c-border: #e2e6ea;
   --c-border-image: #adb5bd;
   --c-gradient-line: var(--c-gradient-main);
   --c-gradient-header: var(--c-gradient-main);
   --c-shadow-main: rgba(0, 0, 0, 0.05);
   --c-shadow-hover: rgba(0, 0, 0, 0.1);
   --c-shadow-tab: rgba(0, 0, 0, 0.1);
 }
 [data-theme="dark"] {
   --c-bg: #121212;
   --c-bg-content: #1e1e1e;
   --c-bg-content-area: #2c2c2c;
   --c-bg-tab: #2c2c2c;
   --c-bg-tab-hover: rgba(0, 198, 255, 0.15);
   --c-text-primary: #ffffff;
   --c-text-secondary: #e9ecef;
   --c-text-muted: #adb5bd;
   --c-text-tab: #adb5bd;
   --c-text-tab-hover: var(--c-blue-secondary);
   --c-text-tab-active: #121212;
   --c-border: #444;
   --c-border-image: #555;
   --c-shadow-main: rgba(0, 0, 0, 0.5);
   --c-shadow-hover: rgba(0, 0, 0, 0.7);
   --c-shadow-tab: rgba(0, 0, 0, 0.4);
 }
 body {
   box-sizing: border-box;
   font-family: 'Kanit', sans-serif;
   background: var(--c-bg);
   min-height: 100%;
   line-height: 1.7;
   margin: 0;
   padding: 0;
   transition: background 0.3s;
 }
 .history-hero-header {
   background: var(--c-gradient-main);
   padding-top: 9rem;
   padding-bottom: 6rem;
   padding-left: 1rem;
   padding-right: 1rem;
   color: white;
   margin-bottom: 0;
   box-shadow: 0 5px 20px rgba(0, 0, 0, 0.2);
   position: relative;
   overflow: visible;
   border-bottom-left-radius: 50px;
   border-bottom-right-radius: 50px;
   z-index: 1;
 }
 .hero-main-title {
   font-weight: 700;
   font-size: 3rem;
   text-shadow: 0 3px 6px rgba(0, 0, 0, 0.2);
   margin-top: 0;
   margin-bottom: 0.5rem;
 }
 .hero-subtitle {
   font-weight: 300;
   font-size: 1.2rem;
   opacity: 0.9;
   margin-top: 0;
   margin-bottom: 0;
 }
 .main-content-overlap {
   position: relative;
   z-index: 10;
   margin-top: -4rem;
   padding-bottom: 50px;
 }
 .tab-menu-container {
   display: flex;
   justify-content: center;
   margin-bottom: 1.875rem;
   background: var(--c-bg-tab);
   border-radius: 3.125rem;
   padding: 0.5rem;
   box-shadow: 0 0.25rem 1rem var(--c-shadow-tab);
   border: 1px solid var(--c-border);
   position: sticky;
   top: 5.5rem;
   z-index: 99;
   backdrop-filter: blur(8px);
   -webkit-backdrop-filter: blur(8px);
 }
 .tab-menu {
   display: flex;
   list-style: none;
   margin: 0;
   padding: 0;
   gap: 0.25rem;
 }
 .tab-item {
   margin: 0;
 }
 .tab-link {
   display: block;
   padding: 0.75rem 1.5rem;
   text-decoration: none;
   color: var(--c-text-tab);
   font-weight: 500;
   font-size: 1rem;
   border-radius: 2.5rem;
   transition: all 0.3s ease;
   white-space: nowrap;
   position: relative;
   background: transparent;
 }
 .tab-link:hover {
   color: var(--c-text-tab-hover);
   background: var(--c-bg-tab-hover);
   text-decoration: none;
 }
 .tab-link.active {
   color: var(--c-text-tab-active);
   background: var(--c-bg-tab-active);
   font-weight: 600;
   box-shadow: 0 0.25rem 1rem rgba(0, 78, 146, 0.4);
 }
 .tab-link.active:hover {
   color: var(--c-text-tab-active);
   background: var(--c-bg-tab-active);
 }
 .content-card {
   background: var(--c-bg-content);
   margin: 2.5rem 0;
   padding: 3.125rem;
   border-radius: 1.5rem;
   border: 1px solid var(--c-border);
   box-shadow: 0 0.5rem 2rem var(--c-shadow-main);
   transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
   position: relative;
   overflow: hidden;
   z-index: 1;
 }
 .content-card::before {
   content: '';
   position: absolute;
   top: 0;
   left: 0;
   right: 0;
   height: 0.35rem;
   background: var(--c-gradient-header);
   border-radius: 1.5rem 1.5rem 0 0;
 }
 .section-title {
   color: var(--c-blue-primary);
   font-weight: 700;
   margin-bottom: 1.875rem;
   position: relative;
   padding-bottom: 0.9375rem;
   font-size: 2rem;
   letter-spacing: -0.5px;
   display: flex;
   align-items: center;
 }
 .section-title i {
   color: var(--c-blue-secondary);
 }
 .section-title::after {
   content: '';
   position: absolute;
   bottom: 0;
   left: 0;
   width: 5rem;
   height: 0.25rem;
   background: var(--c-gradient-line);
   border-radius: 2px;
 }
 .content-area-modern {
   background: var(--c-bg-content-area);
   border: 1px solid var(--c-border);
   border-radius: 0.75rem;
   padding: 1.875rem;
   min-height: 9.375rem;
   color: var(--c-text-secondary);
   font-weight: 400;
   margin: 1.25rem 0;
   font-size: 1.1rem;
   line-height: 1.9;
   box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
 }
 .list-modern-bullet li {
   list-style: none;
   padding-left: 0;
   margin-bottom: 8px;
   color: var(--c-text-secondary);
 }
 .list-modern-bullet i {
   color: var(--c-blue-secondary);
 }
 .image-gallery {
   display: grid;
   grid-template-columns: repeat(auto-fit, minmax(15.625rem, 1fr));
   gap: 1.25rem;
   margin: 1.875rem 0;
   padding: 20px;
   background: var(--c-bg-content-area);
   border-radius: 1rem;
   border: 1px solid var(--c-border);
 }
 .image-placeholder {
   background: var(--c-bg-content);
   border: 1px solid var(--c-border-image);
   border-radius: 0.625rem;
   height: 12.5rem;
   display: flex;
   align-items: center;
   justify-content: center;
   color: var(--c-text-muted);
   font-weight: 600;
   transition: all 0.3s ease;
   overflow: hidden;
   box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
 }
 .image-placeholder img {
   width: 100%;
   height: 100%;
   object-fit: cover;
   transition: transform 0.3s ease;
 }
 .image-placeholder:hover img {
   transform: scale(1.08);
 }
 .image-placeholder:hover {
   border-color: var(--c-blue-secondary);
   background: linear-gradient(135deg, var(--c-blue-secondary) 1%, var(--c-blue-primary) 5%);
   box-shadow: 0 5px 20px rgba(0, 198, 255, 0.3);
 }
 .reference-title {
   color: var(--c-blue-primary) !important;
 }
 .reference-box-modern {
   background: var(--c-bg-content-area);
   border: 1px solid var(--c-border);
   border-radius: 0.75rem;
   padding: 1.5rem;
   box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
 }
 .reference-list-modern {
   list-style: none;
   padding: 0;
   margin: 0;
 }
 .reference-list-modern li {
   padding: 0.625rem 0;
   border-bottom: 1px solid var(--c-border);
   font-size: 1rem;
   color: var(--c-text-secondary);
   font-weight: 400;
   transition: color 0.3s;
 }
 .reference-list-modern li:hover {
   color: var(--c-blue-secondary);
 }
 .reference-list-modern li:last-child {
   border-bottom: none;
 }
 .scroll-to-top {
   position: fixed;
   bottom: 1.875rem;
   right: 1.875rem;
   width: 3.75rem;
   height: 3.75rem;
   background: var(--c-bg-scroll-top);
   color: white;
   border: none;
   border-radius: 50%;
   cursor: pointer;
   display: flex;
   align-items: center;
   justify-content: center;
   font-size: 1.5rem;
   box-shadow: 0 0.5rem 2rem rgba(0, 78, 146, 0.4);
   transition: all 0.3s ease;
   opacity: 0;
   visibility: hidden;
   z-index: 1000;
 }
 .scroll-to-top.show {
   opacity: 1;
   visibility: visible;
 }
 .scroll-to-top:hover {
   transform: translateY(-4px) scale(1.1);
   background: var(--c-bg-scroll-top);
   box-shadow: 0 1rem 3rem rgba(0, 78, 146, 0.5);
 }
 @media (max-width: 768px) {
   body {
     padding-top: 0;
   }
   .history-hero-header {
     padding-top: 6rem;
     padding-bottom: 4rem;
     border-bottom-left-radius: 30px;
     border-bottom-right-radius: 30px;
     margin-bottom: 0;
   }
   .hero-main-title {
     font-size: 2rem;
   }
   .hero-subtitle {
     font-size: 1rem;
     margin-top: 0.5rem;
   }
   .main-content-overlap {
     position: relative;
     z-index: 10;
     margin-top: -2.5rem !important;
   }
   .content-card {
     margin: 1.25rem 0;
     padding: 1.5rem;
     border-radius: 1rem;
   }
   .content-card::before {
     height: 0.25rem;
   }
   .section-title {
     font-size: 1.5rem;
     padding-bottom: 0.75rem;
     margin-bottom: 1.25rem;
   }
   .section-title::after {
     width: 4rem;
     height: 0.15rem;
   }
   .content-area-modern {
     padding: 1rem;
     font-size: 1rem;
     line-height: 1.8;
   }
   .image-gallery {
     grid-template-columns: 1fr;
     padding: 10px;
   }
   .image-placeholder {
     height: 10rem;
   }
   .tab-menu-container {
     margin: 0 0.625rem 1.875rem 0.625rem;
     padding: 0.375rem;
     position: static;
     top: auto;
   }
   .tab-menu {
     flex-wrap: wrap;
     justify-content: center;
     gap: 2px;
   }
   .tab-link {
     padding: 0.5rem 0.75rem;
     font-size: 0.85rem;
   }
   .scroll-to-top {
     bottom: 1.25rem;
     right: 1.25rem;
     width: 3.125rem;
     height: 3.125rem;
     font-size: 1.25rem;
   }
 }