/* ============================================
   CSS Color Variables
   ============================================ */
:root {
    /* Primary Brand Colors */
    --color-primary: #820000;
    --color-primary-dark: #600000;
    
    /* Text Colors */
    --color-text-dark: #333;
    --color-text-medium: #555;
    --color-text-light: #666;
    --color-text-subtle: #999;
    --color-text-black: #000;
    --color-text-white: white;
    
    /* Background Colors */
    --color-bg-light: #fafbfc;
    --color-bg-white: white;
    --color-bg-gray: #f0f0f0;
    
    /* Border Colors */
    --color-border-light: #e0e0e0;
    
    /* Shadows and Transparency */
    --shadow-light: 0 2px 8px rgba(0, 0, 0, 0.05);
    --shadow-medium: 0 4px 15px rgba(0, 0, 0, 0.08);
    --shadow-hover: 0 10px 30px rgba(0, 0, 0, 0.15);
    --shadow-card: 0 10px 30px rgba(0, 0, 0, 0.3);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, sans-serif;
    color: var(--color-text-dark);
    background: var(--color-bg-light);
    padding-top: 70px;
}

/* Navigation */
nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: var(--color-bg-white);
    box-shadow: var(--shadow-medium);
    z-index: 1000;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 50px;
    height: 70px;
}

.nav-logo {
    height: 40px;
    width: auto;
}

.nav-links {
    display: flex;
    gap: 40px;
    list-style: none;
}

.nav-links a {
    text-decoration: none;
    color: var(--color-text-dark);
    font-size: 14px;
    font-weight: 500;
    transition: color 0.3s;
}

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

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--color-primary) 0%, #a00000 100%);
    color: var(--color-text-white);
    padding: 100px 50px;
    text-align: center;
    background-attachment: fixed;
    background-size: cover;
}

.hero-content {
    max-width: 900px;
    margin: 0 auto;
}

.hero-profile {
    width: 150px;
    height: 150px;
    border-radius: 50%;
    margin: 0 auto 30px;
    border: 5px solid var(--color-text-white);
    overflow: hidden;
    box-shadow: var(--shadow-card);
}

.hero-profile img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.hero h1 {
    font-size: 48px;
    margin-bottom: 15px;
    font-weight: 700;
}

.hero .subtitle {
    font-size: 22px;
    margin-bottom: 20px;
    font-weight: 300;
    opacity: 0.95;
}

.hero .research-focus {
    font-size: 15px;
    line-height: 1.8;
    opacity: 0.9;
    margin-bottom: 30px;
}

.cta-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
    flex-wrap: wrap;
}

.cta-btn {
    display: inline-block;
    padding: 12px 30px;
    border-radius: 50px;
    text-decoration: none;
    font-size: 14px;
    font-weight: 600;
    transition: all 0.3s;
    border: 2px solid var(--color-text-white);
}

.cta-btn-primary {
    background: var(--color-text-white);
    color: var(--color-primary);
}

.cta-btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
}

.cta-btn-secondary {
    background: transparent;
    color: var(--color-text-white);
}

.cta-btn-secondary:hover {
    background: rgba(255, 255, 255, 0.1);
}

/* Container */
.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 100px 50px;
}

/* Sections */
.section {
    margin-bottom: 120px;
}

.section-title {
    font-size: 36px;
    color: var(--color-primary);
    margin-bottom: 40px;
    position: relative;
    padding-bottom: 20px;
}

.section-title:after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 60px;
    height: 4px;
    background: var(--color-primary);
}

/* Cards */
.cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-bottom: 40px;
}

.card {
    background: var(--color-bg-white);
    padding: 30px;
    border-radius: 10px;
    box-shadow: var(--shadow-medium);
    transition: all 0.3s;
}

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

.card h3 {
    color: var(--color-primary);
    font-size: 18px;
    margin-bottom: 8px;
}

.card .label {
    color: var(--color-text-subtle);
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 12px;
}

.card p {
    color: var(--color-text-medium);
    font-size: 14px;
    line-height: 1.7;
    margin-bottom: 12px;
}

.card .date {
    color: var(--color-text-subtle);
    font-size: 13px;
    font-style: italic;
}

/* Two Column Layout */
.two-column {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 50px;
}

.column {
    display: flex;
    flex-direction: column;
    gap: 30px;
}

.info-block {
    background: var(--color-bg-white);
    padding: 25px;
    border-radius: 8px;
    box-shadow: var(--shadow-light);
}

.info-block h3 {
    color: var(--color-text-black);
    font-size: 16px;
    margin-bottom: 8px;
    font-weight: 600;
}

.info-block p {
    color: var(--color-text-light);
    font-size: 14px;
    line-height: 1.7;
}

/* Skills */
.skills-list {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 15px;
}

.skill-tag {
    background: var(--color-bg-gray);
    color: var(--color-text-dark);
    padding: 10px 15px;
    border-radius: 20px;
    font-size: 13px;
    border-left: 3px solid var(--color-primary);
}

/* Publications */
.publication {
    background: var(--color-bg-white);
    padding: 20px;
    border-radius: 8px;
    border-left: 4px solid var(--color-primary);
    margin-bottom: 20px;
    box-shadow: var(--shadow-light);
}

.publication h4 {
    color: var(--color-primary);
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 8px;
}

.publication .authors {
    color: var(--color-text-medium);
    font-size: 13px;
    margin-bottom: 8px;
    line-height: 1.5;
}

.publication .venue {
    color: var(--color-text-subtle);
    font-size: 12px;
    font-style: italic;
}

/* Buttons */
.btn-group {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    margin-top: 30px;
}

.btn {
    display: inline-block;
    padding: 10px 20px;
    background: var(--color-primary);
    color: var(--color-text-white);
    text-decoration: none;
    border-radius: 5px;
    font-size: 13px;
    font-weight: 600;
    transition: all 0.3s;
    border: none;
    cursor: pointer;
}

.btn:hover {
    background: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(130, 0, 0, 0.3);
}

.btn-outline {
    background: transparent;
    border: 2px solid var(--color-primary);
    color: var(--color-primary);
}

.btn-outline:hover {
    background: var(--color-primary);
    color: var(--color-text-white);
}

/* Footer */
footer {
    background: var(--color-primary);
    color: var(--color-text-white);
    padding: 50px;
    margin-top: 100px;
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 40px;
}

.footer-logo {
    flex-shrink: 0;
}

.footer-logo img {
    height: 60px;
    width: auto;
}

.footer-content {
    flex: 1;
}

.footer-content p {
    line-height: 1.8;
    font-size: 14px;
    opacity: 0.9;
    color: var(--color-text-white);
}

.social-links {
    display: flex;
    gap: 20px;
    margin-top: 15px;
}

.social-links a {
    color: var(--color-text-white);
    text-decoration: none;
    font-size: 13px;
    font-weight: 600;
    padding: 8px 15px;
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 20px;
    transition: all 0.3s;
}

.social-links a:hover {
    border-color: var(--color-text-white);
    background: rgba(255, 255, 255, 0.1);
}

/* Responsive */
@media (max-width: 768px) {
    nav {
        padding: 0 20px;
    }
    
    .nav-links {
        gap: 20px;
    }
    
    .hero {
        padding: 60px 20px;
    }
    
    .hero h1 {
        font-size: 32px;
    }
    
    .hero .subtitle {
        font-size: 18px;
    }
    
    .container {
        padding: 50px 20px;
    }
    
    .section {
        text-align: center;
    }
    
    .section-title {
        font-size: 28px;
    }
    
    .section-title:after {
        left: 50%;
        transform: translateX(-50%);
    }
    
    .two-column {
        grid-template-columns: 1fr;
        gap: 30px;
    }
    
    .info-block {
        text-align: center;
    }
    
    .card {
        text-align: center;
    }
    
    .publication {
        text-align: center;
        border-left: none;
        border-top: 4px solid var(--color-primary);
    }
    
    .btn-group {
        justify-content: center;
    }
    
    .skills-list {
        grid-template-columns: 1fr;
    }
    
    footer {
        flex-direction: column;
        text-align: center;
        align-items: center;
    }
    
    .footer-logo {
        margin: 0 auto;
        text-align: center;
    }
    
    .footer-logo img {
        margin: 0 auto;
    }
    
    .footer-content {
        text-align: center;
    }
    
    footer > div[style*="text-align: right"] {
        text-align: center !important;
    }
    
    .social-links {
        justify-content: center;
        flex-wrap: wrap;
    }
    
    .container {
        padding: 30px;
    }
    
    header {
        grid-template-columns: 1fr;
    }
    
    .content {
        grid-template-columns: 1fr;
    }
}