:root {
    --bg-primary: #FAFAFA;
    --bg-secondary: #FFFFFF;
    --text-primary: #1A1A1A;
    --text-secondary: #666666;
    --accent: #2563EB;
    --border: #EAEAEA;
    
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body.dark-mode {
    --bg-primary: #121212;
    --bg-secondary: #1E1E1E;
    --text-primary: #FFFFFF;
    --text-secondary: #A0A0A0;
    --border: #333333;
}

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

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: var(--font-sans);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 2rem 0;
    margin-bottom: 4rem;
}

.theme-toggle {
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    transition: background-color var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    background-color: var(--border);
}

nav {
    display: flex;
    gap: 1.5rem;
}

nav a {
    text-decoration: none;
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 500;
    transition: color var(--transition);
}

nav a:hover {
    color: var(--text-primary);
}

.hero {
    margin-bottom: 6rem;
    animation: fadeIn 0.8s ease-out;
}

.hero h1 {
    font-size: 2.5rem;
    font-weight: 600;
    letter-spacing: -0.03em;
    line-height: 1.2;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.hero .subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
    max-width: 600px;
}

.search-container {
    margin-bottom: 2.5rem;
}

.search-input {
    width: 100%;
    padding: 1rem 1.5rem;
    font-size: 1rem;
    font-family: var(--font-sans);
    color: var(--text-primary);
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    outline: none;
    transition: border-color var(--transition), box-shadow var(--transition);
}

.search-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.articles-grid {
    display: flex;
    flex-direction: column;
    gap: 2.5rem;
}

.article-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 2rem;
    transition: transform var(--transition), box-shadow var(--transition);
    opacity: 0;
    transform: translateY(10px);
    animation: fadeIn 0.8s ease-out forwards;
    display: block;
    text-decoration: none;
    color: inherit;
}

.article-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 24px -10px rgba(0, 0, 0, 0.08);
}

.article-category {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.75rem;
    display: block;
}

.article-title {
    font-size: 1.5rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
    line-height: 1.3;
}

.article-excerpt {
    color: var(--text-secondary);
    font-size: 1rem;
    line-height: 1.6;
}

footer {
    margin-top: 6rem;
    padding: 2rem 0;
    border-top: 1px solid var(--border);
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@media (max-width: 600px) {
    header {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }
    
    .hero h1 {
        font-size: 2rem;
    }
}