:root {
    --tech-blue: #0074D9;
    --silver-gray: #BDC3C7;
    --bright-yellow: #F1C40F;
    --dark-blue: #003366;
    --light-gray: #F5F7FA;
    --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

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

body {
    font-family: 'Roboto', sans-serif;
    line-height: 1.6;
    color: #333;
    background: var(--light-gray);
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.header {
    background: linear-gradient(135deg, var(--tech-blue), var(--dark-blue));
    color: white;
    padding: 2rem 0;
    text-align: center;
    position: relative;
    overflow: hidden;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://images.gptkong.com/demo/sample1.png') center/cover no-repeat;
    opacity: 0.1;
    z-index: 0;
}

.header h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    position: relative;
    z-index: 1;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

.header p {
    font-size: 1.2rem;
    max-width: 800px;
    margin: 0 auto;
    position: relative;
    z-index: 1;
}

.navbar {
    position: sticky;
    top: 0;
    background: rgba(0, 51, 102, 0.95);
    z-index: 1000;
    display: flex;
    justify-content: center;
    padding: 1rem 0;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(5px);
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: var(--transition);
    position: relative;
}

.nav-links a:hover {
    color: var(--bright-yellow);
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 0;
    height: 2px;
    background: var(--bright-yellow);
    transition: var(--transition);
}

.nav-links a:hover::after {
    width: 100%;
}

.main-content {
    padding: 3rem 0;
}

.section {
    background: white;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
    padding: 2rem;
    margin-bottom: 3rem;
    position: relative;
    overflow: hidden;
}

.section::after {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 100px;
    height: 100px;
    background: url('https://images.gptkong.com/demo/sample2.png') center/cover no-repeat;
    opacity: 0.1;
    z-index: 0;
}

.section h2 {
    color: var(--tech-blue);
    margin-bottom: 1.5rem;
    position: relative;
    z-index: 1;
    font-size: 1.8rem;
}

.section h3 {
    color: var(--dark-blue);
    margin: 1.5rem 0 1rem;
    position: relative;
    z-index: 1;
    font-size: 1.4rem;
}

.section p {
    margin-bottom: 1rem;
    position: relative;
    z-index: 1;
}

.code-container {
    background: #282c34;
    border-radius: 6px;
    padding: 1rem;
    margin: 1.5rem 0;
    overflow: auto;
    position: relative;
}

.code-container pre {
    margin: 0;
    font-family: 'Courier New', monospace;
    color: #abb2bf;
    line-height: 1.5;
    white-space: pre-wrap;
}

.code-container code {
    display: block;
    font-size: 0.9rem;
}

.image-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
}

.image-card {
    background: white;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
    transition: var(--transition);
    position: relative;
}

.image-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
}

.image-card img {
    width: 100%;
    height: 200px;
    object-fit: cover;
    display: block;
}

.image-card .caption {
    padding: 1rem;
    background: white;
}

.image-card .caption h4 {
    color: var(--tech-blue);
    margin-bottom: 0.5rem;
}

.footer {
    background: linear-gradient(135deg, var(--dark-blue), var(--tech-blue));
    color: white;
    text-align: center;
    padding: 2rem 0;
    margin-top: 3rem;
}

.footer p {
    margin-bottom: 0.5rem;
}

.notice {
    background: var(--bright-yellow);
    color: var(--dark-blue);
    padding: 1rem;
    text-align: center;
    font-weight: bold;
    margin-bottom: 2rem;
    border-radius: 4px;
}

@media (max-width: 768px) {
    .header h1 {
        font-size: 2rem;
    }
    
    .nav-links {
        flex-direction: column;
        gap: 0.5rem;
        align-items: center;
    }
    
    .image-grid {
        grid-template-columns: 1fr;
    }
}

/* Animation classes */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.animate {
    animation: fadeIn 0.8s ease-out forwards;
}

.delay-1 { animation-delay: 0.2s; }
.delay-2 { animation-delay: 0.4s; }
.delay-3 { animation-delay: 0.6s; }

/* Parallax effect */
.parallax-section {
    background-attachment: fixed;
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    min-height: 400px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    color: white;
    text-align: center;
    margin: 3rem 0;
}

.parallax-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 51, 102, 0.7);
}

.parallax-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
    padding: 2rem;
}

/* Collapsible sections */
.collapsible {
    background-color: var(--tech-blue);
    color: white;
    cursor: pointer;
    padding: 1rem;
    width: 100%;
    border: none;
    text-align: left;
    outline: none;
    font-size: 1.1rem;
    border-radius: 4px;
    margin: 1rem 0;
    transition: var(--transition);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.collapsible:hover {
    background-color: var(--dark-blue);
}

.collapsible::after {
    content: '+';
    font-weight: bold;
    font-size: 1.2rem;
}

.collapsible.active::after {
    content: '-';
}

.content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease-out;
    background-color: #f9f9f9;
    border-radius: 0 0 4px 4px;
}

.collapsible.active + .content {
    max-height: 1000px;
    padding: 1rem;
    border: 1px solid #ddd;
    border-top: none;
}