:root {
    --primary-color: #1E90FF;
    --secondary-color: #32CD32;
    --accent-color: #FF6B6B;
    --neutral-light: #F5F5F5;
    --neutral-dark: #333333;
    --gradient-blue: linear-gradient(135deg, #1E90FF 0%, #4682B4 100%);
    --gradient-green: linear-gradient(135deg, #32CD32 0%, #28A745 100%);
    --shadow-sm: 0 4px 6px rgba(0,0,0,0.1);
    --shadow-md: 0 10px 15px rgba(0,0,0,0.1);
    --shadow-lg: 0 20px 25px rgba(0,0,0,0.1);
    --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

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

html {
    scroll-behavior: smooth;
}

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

/* Header Styles */
.header {
    background: var(--gradient-blue);
    color: white;
    padding: 2rem 0;
    position: relative;
    overflow: hidden;
    margin-bottom: 3rem;
}

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

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    position: relative;
    z-index: 1;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.notice-banner {
    background: rgba(255,255,255,0.2);
    padding: 0.5rem 1rem;
    border-radius: 4px;
    margin-bottom: 1rem;
    font-size: 0.9rem;
    align-self: center;
}

/* Navigation */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    background: var(--gradient-blue);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

.nav-logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: white;
    text-decoration: none;
}

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

.nav-item {
    margin-left: 2rem;
    position: relative;
}

.nav-link {
    color: white;
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: white;
    transition: var(--transition);
}

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

/* Main Content */
.main-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: grid;
    grid-template-columns: 250px 1fr;
    gap: 2rem;
}

.sidebar {
    position: sticky;
    top: 100px;
    align-self: start;
    background: white;
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: var(--shadow-sm);
}

.sidebar-title {
    font-size: 1.2rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
    position: relative;
    padding-bottom: 0.5rem;
}

.sidebar-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 50px;
    height: 3px;
    background: var(--gradient-green);
}

.sidebar-nav {
    list-style: none;
}

.sidebar-item {
    margin-bottom: 0.75rem;
}

.sidebar-link {
    color: var(--neutral-dark);
    text-decoration: none;
    transition: var(--transition);
    display: block;
    padding: 0.5rem 0;
    position: relative;
}

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

.sidebar-link:hover {
    color: var(--secondary-color);
}

.sidebar-link:hover::before {
    width: 100%;
}

.content {
    background: white;
    border-radius: 8px;
    padding: 2rem;
    box-shadow: var(--shadow-sm);
    margin-bottom: 3rem;
}

/* Article Styles */
article {
    max-width: 800px;
    margin: 0 auto;
}

article h2 {
    font-size: 2rem;
    margin: 2rem 0 1rem;
    color: var(--primary-color);
    position: relative;
    padding-bottom: 0.5rem;
}

article h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 80px;
    height: 4px;
    background: var(--gradient-green);
}

article h3 {
    font-size: 1.5rem;
    margin: 1.5rem 0 1rem;
    color: var(--neutral-dark);
}

article p {
    margin-bottom: 1.5rem;
    font-size: 1.1rem;
    line-height: 1.8;
}

/* Code Blocks */
pre {
    background: #282c34;
    border-radius: 8px;
    padding: 1.5rem;
    margin: 1.5rem 0;
    overflow: auto;
    box-shadow: var(--shadow-sm);
}

code {
    font-family: 'Courier New', monospace;
    color: #abb2bf;
    font-size: 0.9rem;
}

/* Tables */
table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
    box-shadow: var(--shadow-sm);
}

th, td {
    padding: 1rem;
    text-align: left;
    border: 1px solid #ddd;
}

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

tr:nth-child(even) {
    background: rgba(30, 144, 255, 0.05);
}

/* Images */
.article-img {
    width: 100%;
    border-radius: 8px;
    margin: 1.5rem 0;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.article-img:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

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

.img-grid-item {
    border-radius: 8px;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.img-grid-item:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

/* Cards */
.card {
    background: white;
    border-radius: 8px;
    padding: 1.5rem;
    margin: 1.5rem 0;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

.card-title {
    font-size: 1.2rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

/* Footer */
.footer {
    background: var(--gradient-blue);
    color: white;
    padding: 3rem 0;
    text-align: center;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* Responsive */
@media (max-width: 992px) {
    .main-container {
        grid-template-columns: 1fr;
    }
    
    .sidebar {
        position: static;
        margin-bottom: 2rem;
    }
}

@media (max-width: 768px) {
    .navbar {
        flex-direction: column;
        padding: 1rem;
    }
    
    .nav-menu {
        margin-top: 1rem;
    }
    
    .nav-item {
        margin-left: 1rem;
    }
    
    .header-content {
        padding: 0 1rem;
    }
    
    .main-container {
        padding: 0 1rem;
    }
}

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

.animate {
    animation: fadeIn 0.6s ease-out forwards;
}

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