/* Light mode variables */
:root {
    --bg-color: #fdfdfd;
    --text-color: #333;
    --header-border: #e74c3c;
    --accent-color: #e74c3c;
    --secondary-color: #34495e;
    --meta-color: #95a5a6;
    --subtitle-color: #7f8c8d;
    --stats-bg: #ecf0f1;
    --methodology-bg: #f8f9fa;
    --key-finding-bg: #e8f5e8;
    --timeline-bg: white;
    --timeline-border: #ecf0f1;
    --authors-bg: #34495e;
    --authors-text: white;
    --shadow-color: rgba(0,0,0,0.1);
}

/* Dark mode variables */
[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --text-color: #e0e0e0;
    --header-border: #e74c3c;
    --accent-color: #ff6b6b;
    --secondary-color: #4a90a4;
    --meta-color: #a0a0a0;
    --subtitle-color: #b0b0b0;
    --stats-bg: #2d2d2d;
    --methodology-bg: #2a2a2a;
    --key-finding-bg: #1e3a1e;
    --timeline-bg: #2d2d2d;
    --timeline-border: #3d3d3d;
    --authors-bg: #2a2a2a;
    --authors-text: #e0e0e0;
    --shadow-color: rgba(255,255,255,0.1);
}

body { 
    font-family: 'Georgia', 'Times New Roman', serif; 
    line-height: 1.7; 
    margin: 0; 
    background: var(--bg-color); 
    color: var(--text-color);
    transition: background-color 0.3s ease, color 0.3s ease;
}

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

.header {
    text-align: center;
    margin-bottom: 3em;
    border-bottom: 2px solid var(--header-border);
    padding-bottom: 2em;
}

.theme-toggle {
    position: absolute;
    top: 2em;
    right: 2em;
    background: var(--accent-color);
    color: white;
    border: none;
    padding: 0.7em 1.2em;
    border-radius: 25px;
    cursor: pointer;
    font-size: 0.9em;
    font-weight: bold;
    transition: all 0.3s ease;
    box-shadow: 0 2px 4px var(--shadow-color);
}

.theme-toggle:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px var(--shadow-color);
}

h1 { 
    color: var(--accent-color); 
    font-size: 2.5em; 
    margin-bottom: 0.5em;
    font-weight: 300;
}

.subtitle {
    font-size: 1.2em;
    color: var(--subtitle-color);
    font-style: italic;
    margin-bottom: 1em;
}

.meta {
    color: var(--meta-color);
    font-size: 0.9em;
}

h2 { 
    color: var(--accent-color); 
    font-size: 1.8em;
    margin-top: 2em;
    margin-bottom: 1em;
}

h3 { 
    color: var(--secondary-color); 
    font-size: 1.3em;
    margin-top: 1.5em;
}

.highlight {
    background: linear-gradient(120deg, #f39c12 0%, #f39c12 100%);
    background-repeat: no-repeat;
    background-size: 100% 0.2em;
    background-position: 0 88%;
    padding: 2px 0;
}

.stats {
    background: var(--stats-bg);
    border-radius: 8px;
    padding: 1.5em;
    margin: 2em 0;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1em;
    transition: background-color 0.3s ease;
}

.stat-item {
    text-align: center;
}

.stat-number {
    font-size: 2em;
    font-weight: bold;
    color: var(--accent-color);
    display: block;
}

.stat-label {
    color: var(--subtitle-color);
    font-size: 0.9em;
}

.methodology {
    background: var(--methodology-bg);
    border-left: 4px solid #3498db;
    padding: 1.5em;
    margin: 2em 0;
    transition: background-color 0.3s ease;
}

.key-finding {
    background: var(--key-finding-bg);
    border-left: 4px solid #27ae60;
    padding: 1.5em;
    margin: 1.5em 0;
    border-radius: 0 8px 8px 0;
    transition: background-color 0.3s ease;
}

.tech-stack {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5em;
    margin: 1em 0;
}

.tech-badge {
    background: #3498db;
    color: white;
    padding: 0.3em 0.8em;
    border-radius: 20px;
    font-size: 0.8em;
    font-weight: bold;
}

.authors {
    background: var(--authors-bg);
    color: var(--authors-text);
    padding: 2em;
    border-radius: 8px;
    margin-top: 3em;
    text-align: center;
    transition: background-color 0.3s ease;
}

.authors h3 {
    color: var(--authors-text);
    margin-top: 0;
}

.author-link {
    color: #3498db;
    text-decoration: none;
    font-weight: bold;
}

.author-link:hover {
    color: #5dade2;
}

.cta {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 2em;
    border-radius: 12px;
    text-align: center;
    margin: 2em 0;
}

.cta h3 {
    color: white;
    margin-top: 0;
}

.btn {
    display: inline-block;
    background: white;
    color: #667eea;
    padding: 0.8em 2em;
    text-decoration: none;
    border-radius: 25px;
    font-weight: bold;
    margin: 0.5em;
    transition: transform 0.2s;
}

.btn:hover {
    transform: translateY(-2px);
}

.timeline {
    position: relative;
    margin: 2em 0;
}

.timeline-item {
    background: var(--timeline-bg);
    border: 1px solid var(--timeline-border);
    border-radius: 8px;
    padding: 1.5em;
    margin-bottom: 1em;
    box-shadow: 0 2px 4px var(--shadow-color);
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.timeline-item h4 {
    color: var(--accent-color);
    margin-top: 0;
}

@media (max-width: 768px) {
    .container { padding: 1em; }
    h1 { font-size: 2em; }
    .stats { grid-template-columns: 1fr; }
    .theme-toggle {
        position: relative;
        top: 0;
        right: 0;
        margin-bottom: 1em;
    }
}