:root {
    --primary-color: #003366; /* Deep blue for a professional, scientific feel */
    --secondary-color: #4A90E2; /* A brighter blue for accents and links */
    --background-color: #fdfdfd; /* A slightly softer white */
    --light-gray: #f0f2f5;
    --text-color: #333;
    --heading-font: 'Georgia', 'Times New Roman', serif;
    --body-font: 'Roboto', 'Segoe UI', -apple-system, BlinkMacSystemFont, sans-serif;
}

body {
    font-family: var(--body-font);
    color: var(--text-color);
    background-color: var(--background-color);
    scroll-behavior: smooth;
    line-height: 1.7;
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--heading-font);
    font-weight: 700;
    color: var(--primary-color);
}

.navbar {
    background-color: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(12px);
    box-shadow: 0 2px 8px rgba(0,0,0,0.07);
    transition: background-color 0.3s ease;
}

.navbar-brand {
    font-family: var(--heading-font);
    font-weight: bold;
    color: var(--primary-color) !important;
}

.nav-link {
    transition: color 0.3s ease;
}

.nav-link:hover, .nav-link.active {
    color: var(--secondary-color) !important;
}

/* --- Hero Section --- */
.hero-section {
    background: var(--background-color);
    padding: 100px 0;
    min-height: 90vh;
    display: flex;
    align-items: center;
}

.profile-img {
    width: 280px;
    height: 280px;
    object-fit: cover;
    border-radius: 50%;
    border: 5px solid var(--light-gray);
    box-shadow: 0 10px 30px rgba(0, 51, 102, 0.15);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.profile-img:hover {
    transform: scale(1.05);
    box-shadow: 0 15px 40px rgba(74, 144, 226, 0.2);
}

.hero-section .display-4 {
    font-size: 3.5rem;
    font-weight: 700;
}

.lead {
    font-size: 1.5rem;
    color: var(--secondary-color);
    font-family: var(--heading-font);
    font-weight: 400;
}

.btn-primary {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    padding: 12px 25px;
    transition: all 0.3s ease;
}

.btn-primary:hover {
    background-color: #002244; /* Darker shade */
    border-color: #002244;
    transform: translateY(-2px);
}

.btn-outline-secondary {
    border-color: var(--secondary-color);
    color: var(--secondary-color);
    padding: 12px 25px;
    transition: all 0.3s ease;
}

.btn-outline-secondary:hover {
    background-color: var(--secondary-color);
    color: white;
    transform: translateY(-2px);
}


/* --- Section Styling --- */
section {
    padding: 80px 0;
}

#research, #education {
    background-color: var(--light-gray);
}

.section-title {
    padding-bottom: 3rem;
    text-align: center;
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: 2.5rem;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background-color: var(--secondary-color);
}

/* --- Research Section --- */
.research-card {
    background: #fff;
    border: none;
    border-radius: 10px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.05);
    padding: 2.5rem;
}

.research-figure {
    max-width: 100%;
    border-radius: 8px;
    border: 1px solid #dee2e6;
    transition: transform 0.3s ease;
    cursor: pointer;
}

.research-figure:hover {
    transform: scale(1.03);
}

/* --- Skills Section --- */
.skill-card {
    border: none;
    border-radius: 10px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.05);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    background-color: #fff;
}

.skill-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 30px rgba(0,0,0,0.08);
}

.skill-card .card-title {
    text-align: left; /* Aligns the main card titles to the left */
}

.skill-card .card-title i {
    color: var(--secondary-color);
}

.skill-card .card-body p {
    text-align: left; /* Aligns paragraph text to the left */
}


/* --- Education & Experience Section --- */
.timeline {
    list-style: none;
    padding: 0;
    position: relative;
}

.timeline:before {
    content: '';
    position: absolute;
    top: 0;
    bottom: 0;
    left: 12px;
    width: 2px;
    background: #dee2e6;
    margin-left: -1.5px;
}

.timeline-item {
    margin-bottom: 30px;
    position: relative;
    padding-left: 45px;
}

.timeline-icon {
    position: absolute;
    left: 0;
    top: 0;
    width: 25px;
    height: 25px;
    border-radius: 50%;
    background: var(--secondary-color);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    border: 2px solid var(--light-gray);
}

.award-icon {
    color: #ffc107;
}

/* --- Footer --- */
footer {
    background: var(--primary-color);
    color: #e9ecef;
    padding: 60px 0;
}

footer h2 {
    color: white;
}

footer a {
    color: #adb5bd;
    text-decoration: none;
    transition: color 0.3s ease;
}

footer a:hover {
    color: white;
}

.social-icons a {
    font-size: 1.8rem;
    transition: transform 0.3s ease;
    display: inline-block;
}

.social-icons a:hover {
    transform: translateY(-3px);
    color: white;
}