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

    body {
        font-family: 'Sarabun', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        line-height: 1.8;
        color: #1a1a1a;
        background-image: url('img/preview.webp');
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    background-repeat: repeat;
        min-height: 100vh;
        display: flex;
        flex-direction: column;
    }

    /* Navbar */
nav {
    background: linear-gradient(135deg, #2d4a2d 0%, #3d5a3d 50%, #4a6b4a 100%);
    padding: 1rem 2rem;
    box-shadow: 0 2px 10px rgba(0,0,0,0.4);
    position: sticky;
    top: 0;
    z-index: 1000;
    border-bottom: 3px solid #5a7d5a;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    color: #fff;
    font-size: 1.5rem;
    font-weight: bold;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo img {
    width: 70px;
    height: 70px;
    object-fit: contain;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-links a {
    color: #fff;
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: 5px;
    transition: all 0.3s ease;
    background: rgba(0,0,0,0.2);
}

.nav-links a:hover {
    background: rgba(255,255,255,0.2);
    transform: translateY(-2px);
    text-decoration: underline;
}

/* Responsive - ปรับให้สวยบนมือถือ */
@media (max-width: 768px) {
    nav {
        padding: 0.8rem 1rem;
    }
    
    .nav-container {
        flex-direction: column;
        gap: 1rem;
    }
    
    .logo {
        font-size: 1.2rem;
    }
    
    .logo img {
        width: 50px;
        height: 50px;
    }
    
    .nav-links {
        flex-wrap: wrap;
        justify-content: center;
        gap: 0.5rem;
        width: 100%;
    }
    
    .nav-links a {
        padding: 0.5rem 0.8rem;
        font-size: 0.85rem;
        flex: 0 1 auto;
    }
}

@media (max-width: 480px) {
    .logo {
        font-size: 1rem;
    }
    
    .logo img {
        width: 40px;
        height: 40px;
    }
    
    .nav-links a {
        padding: 0.4rem 0.6rem;
        font-size: 0.8rem;
    }
}

    /* Main Content */
    main {
        flex: 1;
        max-width: 1200px;
        margin: 2rem auto;
        padding: 2rem;
        width: 100%;
    }

    .hero-section {
        background: linear-gradient(135deg, rgba(45, 74, 45, 0.95), rgba(61, 90, 61, 0.95));
        color: white;
        padding: 3rem 2rem;
        border-radius: 15px;
        text-align: center;
        margin-bottom: 3rem;
        box-shadow: 0 10px 30px rgba(0,0,0,0.5);
        border: 3px solid #5a7d5a;
    }

    .hero-section h1 {
        font-size: 2.5rem;
        margin-bottom: 0.5rem;
    }

    .hero-section .reign-period {
        font-size: 1.2rem;
        opacity: 0.9;
        margin-top: 1rem;
    }

    .content-grid {
        display: grid;
        grid-template-columns: 1fr 2fr;
        gap: 2rem;
        margin-bottom: 2rem;
    }

    .image-section {
        background: white;
        padding: 2rem;
        border-radius: 15px;
        box-shadow: 0 5px 20px rgba(0,0,0,0.1);
        text-align: center;
    }

    .image-placeholder {
        width: 100%;
        height: 400px;
        background: linear-gradient(135deg, #e0e0e0 0%, #f5f5f5 100%);
        border-radius: 10px;
        display: flex;
        align-items: center;
        justify-content: center;
        color: #666;
        font-size: 1.2rem;
        margin-bottom: 1rem;
    }

    .info-section {
        background: white;
        padding: 2rem;
        border-radius: 15px;
        box-shadow: 0 5px 20px rgba(0,0,0,0.1);
    }

    .info-section h2 {
        color: #2d4a2d;
        margin-bottom: 1rem;
        padding-bottom: 0.5rem;
        border-bottom: 3px solid #4a6b4a;
    }

    .info-item {
        margin-bottom: 1.5rem;
        padding: 1rem;
        background: #f9f9f9;
        border-radius: 8px;
        border-left: 4px solid #4a6b4a;
    }

    .info-item h3 {
        color: #3d5a3d;
        margin-bottom: 0.5rem;
        font-size: 1.1rem;
    }

    .info-item p {
        color: #555;
        line-height: 1.8;
    }

    .content-section {
        background: white;
        padding: 2rem;
        border-radius: 15px;
        box-shadow: 0 5px 20px rgba(0,0,0,0.1);
        margin-bottom: 2rem;
    }

    .content-section h2 {
        color: #2d4a2d;
        margin-bottom: 1.5rem;
        padding-bottom: 0.5rem;
        border-bottom: 3px solid #4a6b4a;
        font-size: 1.8rem;
    }

    .content-section h3 {
        color: #3d5a3d;
        margin-top: 1.5rem;
        margin-bottom: 1rem;
        font-size: 1.3rem;
    }

    .content-section p {
        margin-bottom: 1rem;
        text-indent: 2rem;
    }

    .highlight-box {
        background: linear-gradient(135deg, #f0f5f0 0%, #e8f0e8 100%);
        padding: 1.5rem;
        border-radius: 10px;
        border-left: 5px solid #4a6b4a;
        margin: 1.5rem 0;
    }

    .achievement-list {
        list-style: none;
        padding: 0;
    }

    .achievement-list li {
        padding: 1rem;
        margin-bottom: 0.8rem;
        background: #f9f9f9;
        border-radius: 8px;
        border-left: 4px solid #5a7d5a;
        transition: all 0.3s ease;
    }

    .achievement-list li:hover {
        background: #f0f5f0;
        transform: translateX(5px);
    }

    .achievement-list li::before {
        content: "✦ ";
        color: #4a6b4a;
        font-weight: bold;
        margin-right: 0.5rem;
    }

    /* Footer */
    footer {
        background: linear-gradient(135deg, #2d4a2d 0%, #3d5a3d 50%, #4a6b4a 100%);
        color: white;
        padding: 2rem;
        margin-top: auto;
        border-top: 3px solid #5a7d5a;
    }

    .footer-container {
        max-width: 1200px;
        margin: 0 auto;
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
        gap: 2rem;
    }

    .footer-section h3 {
        margin-bottom: 1rem;
        font-size: 1.2rem;
    }

    .footer-section ul {
        list-style: none;
    }

    .footer-section ul li {
        margin-bottom: 0.5rem;
    }

    .footer-section a {
        color: #fff;
        text-decoration: none;
        opacity: 0.8;
        transition: opacity 0.3s;
    }

    .footer-section a:hover {
        opacity: 1;
    }

    .footer-bottom {
        text-align: center;
        margin-top: 2rem;
        padding-top: 1rem;
        border-top: 1px solid rgba(255,255,255,0.2);
    }

    /* Responsive */
    @media (max-width: 768px) {
        .content-grid {
            grid-template-columns: 1fr;
        }

        .hero-section h1 {
            font-size: 1.8rem;
        }

        .nav-links {
            gap: 1rem;
        }

        .nav-links a {
            padding: 0.3rem 0.7rem;
            font-size: 0.9rem;
        }
    }

    .footer-icon {
        width: 20px;
        height: 20px;
        vertical-align: middle;
        margin-right: 8px;
        filter: brightness(0) invert(1); /* ทำให้รูปเป็นสีขาว */
    }

reference-list {
    margin-left: 1.5rem;
    color: #555;
}

.reference-list li {
    margin-bottom: 0.8rem;
    line-height: 1.6;
}

.reference-list li a {
    color: #3d5a3d;
    text-decoration: none;
    transition: color 0.3s;
}

.reference-list li a:hover {
    color: #4a6b4a;
    text-decoration: underline;
}

  
.image-placeholder {
    width: 100%;
    height: 500px;  /* เพิ่มจาก 400px เป็น 500px */
    background: linear-gradient(135deg, #e0e0e0 0%, #f5f5f5 100%);
    border-radius: 15px;  /* เพิ่มจาก 10px เป็น 15px */
    display: flex;
    align-items: center;
    justify-content: center;
    color: #666;
    font-size: 1.2rem;
    margin-bottom: 1rem;
    overflow: hidden;
}
.reference-list li a:hover {
    color: #4a6b4a;
    text-decoration: underline;
}

/* Literature Section Styles */
.literature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.2rem;
    margin: 1.5rem 0;
}

.literature-item {
    display: flex;
    gap: 1rem;
    padding: 1.2rem;
    background: linear-gradient(135deg, #f9f9f9 0%, #ffffff 100%);
    border-radius: 10px;
    border-left: 4px solid #4a6b4a;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.literature-number {
    flex-shrink: 0;
    width: 45px;
    height: 45px;
    background: linear-gradient(135deg, #4a6b4a 0%, #5a7d5a 100%);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 0.95rem;
    box-shadow: 0 2px 8px rgba(74, 107, 74, 0.3);
}

.literature-content {
    flex: 1;
}

.literature-content h4 {
    color: #2d4a2d;
    margin-bottom: 0.5rem;
    font-size: 1.05rem;
    font-weight: 600;
}

.literature-content p {
    color: #555;
    font-size: 0.95rem;
    line-height: 1.6;
    margin: 0;
    text-indent: 0;
}

/* Responsive adjustments */
@media (max-width: 768px) {
    .literature-grid {
        grid-template-columns: 1fr;
    }
    
    .literature-item {
        padding: 1rem;
    }
    
    .literature-number {
        width: 40px;
        height: 40px;
        font-size: 0.85rem;
    }
}
.literature-item-simple {
    padding: 1rem;
    background: linear-gradient(135deg, #f9f9f9 0%, #ffffff 100%);
    border-radius: 10px;
    border-left: 4px solid #4a6b4a;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
    color: #555;
    line-height: 1.6;
}

.literature-item-simple strong {
    color: #2d4a2d;
}
.literature-number-square {
    flex-shrink: 0;
    padding: 0.6rem 1rem;
    background: linear-gradient(135deg, #4a6b4a 0%, #5a7d5a 100%);
    color: white;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 0.9rem;
    box-shadow: 0 2px 8px rgba(74, 107, 74, 0.3);
    white-space: nowrap;
}

#popup {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 10px;
}
#popup-box {
    background: #2a3c2a;
    padding: 60px 90px;
    border-radius: 10px;
    text-align: center;
    box-shadow: 0 0 10px #4a6b4a;
    border-radius: 10px;
}
.popup-message {
      color: #ffffff; /* Blue */
      font-size: 18px;
      font-weight: bold;
    }
button {
    margin: 10px;
    padding: 8px 16px;
    font-size: 16px;
    cursor: pointer;
    border-radius: 10px;
    color: #2e432e;
}