/* ==== style.css ==== */
:root {
    --beaver-blue: #1e407c;
    --white-out: #ffffff;
    --light-grey: #f8f9fa; /* Subtle background for alternating sections */
    --dark-text: #333333;
    --medium-grey: #5f6368;
    --accent-blue-light: #4a90e2; /* A lighter, brighter blue for highlights */
    --gradient-blue: linear-gradient(135deg, var(--beaver-blue) 0%, var(--accent-blue-light) 100%);

    --font-primary: 'Poppins', sans-serif;
    --font-secondary: 'Open Sans', sans-serif;

    --header-height: 70px;
    --border-radius: 8px;
    --box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
    --transition-speed: 0.3s ease;
}

/* --- Global Resets & Base Styles --- */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px; /* Base font size */
}

body {
    font-family: var(--font-secondary);
    color: var(--dark-text);
    background-color: var(--white-out);
    line-height: 1.7;
    overflow-x: hidden; /* Prevent horizontal scroll */
}

.container {
    width: 90%;
    max-width: 1140px;
    margin: 0 auto;
}

h1, h2, h3, h4 {
    font-family: var(--font-primary);
    color: var(--beaver-blue);
    font-weight: 600;
    line-height: 1.3;
}

h1 { font-size: 3rem; }
h2 { font-size: 2.25rem; } /* Section titles */
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

p { margin-bottom: 1rem; }
a { color: var(--accent-blue-light); text-decoration: none; transition: color var(--transition-speed); }
a:hover { color: var(--beaver-blue); }
ul { list-style: none; }

.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    font-family: var(--font-primary);
    font-weight: 600;
    text-decoration: none;
    border-radius: var(--border-radius);
    transition: all var(--transition-speed);
    cursor: pointer;
    border: 2px solid transparent;
}

.btn-primary {
    background-color: var(--accent-blue-light);
    color: var(--white-out);
    border-color: var(--accent-blue-light);
}
.btn-primary:hover {
    background-color: var(--beaver-blue);
    border-color: var(--beaver-blue);
    transform: translateY(-2px);
}

/* --- Header & Navbar --- */
#header {
    background-color: transparent; /* Initial state */
    padding: 0.5rem 0;
    position: fixed;
    width: 100%;
    top: 0;
    left: 0;
    z-index: 1000;
    transition: background-color var(--transition-speed), box-shadow var(--transition-speed), padding var(--transition-speed);
    height: var(--header-height);
}
#header.scrolled {
    background-color: var(--white-out);
    box-shadow: var(--box-shadow);
    padding: 0.25rem 0; /* Slightly reduce padding on scroll */
}

.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 100%;
}

.logo {
    font-family: var(--font-primary);
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--beaver-blue); /* Always Beaver Blue for visibility */
}
#header.scrolled .logo { color: var(--beaver-blue); }
#header:not(.scrolled) .logo { color: var(--white-out); } /* White on transparent header */


#navbar ul { display: flex; }
#navbar ul li { margin-left: 2rem; }
#navbar ul li a {
    font-family: var(--font-primary);
    font-weight: 500;
    color: var(--beaver-blue); /* Default for solid header */
    padding-bottom: 0.3rem;
    border-bottom: 2px solid transparent;
    transition: color var(--transition-speed), border-bottom-color var(--transition-speed);
}
#header:not(.scrolled) #navbar ul li a { color: var(--white-out); } /* White on transparent header */

#navbar ul li a:hover,
#navbar ul li a.active { /* .active class to be added by JS */
    color: var(--accent-blue-light);
    border-bottom-color: var(--accent-blue-light);
}
#header:not(.scrolled) #navbar ul li a:hover,
#header:not(.scrolled) #navbar ul li a.active {
    color: var(--accent-blue-light); /* Or a very light grey */
    border-bottom-color: var(--accent-blue-light);
}

#mobile-menu-toggle { display: none; /* Hidden on desktop */ }


/* --- Hero Section --- */
#hero {
    height: 100vh;
    min-height: 600px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    position: relative;
    color: var(--white-out);
    /* ==== EDITABLE: Replace with your HD background image ==== */
    /* Suggestion: search "abstract molecular structure blue" or "computational science background" on Unsplash/Pexels */
    background: url('https://images.unsplash.com/photo-1532187863486-abf9db5a9997?q=80&w=2070&auto=format&fit=crop') no-repeat center center/cover;
    margin-top: 0; /* Hero is the first element */
}
.hero-overlay {
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background-color: rgba(30, 64, 124, 0.7); /* Beaver Blue overlay */
    z-index: 1;
}
.hero-content {
    position: relative;
    z-index: 2;
    max-width: 800px;
}
.hero-content h1 {
    color: var(--white-out);
    font-size: 3.5rem; /* Larger for hero */
    margin-bottom: 1rem;
    font-weight: 700;
}
.hero-content .subtitle {
    font-size: 1.3rem;
    margin-bottom: 2rem;
    font-weight: 300;
    color: rgba(255,255,255,0.9);
}
.hero-content .btn-primary {
    background-color: var(--white-out);
    color: var(--beaver-blue);
    border-color: var(--white-out);
    padding: 0.8rem 2rem;
    font-size: 1.1rem;
}
.hero-content .btn-primary:hover {
    background-color: transparent;
    color: var(--white-out);
}

/* --- General Section Styling --- */
.section-padding {
    padding: 80px 0; /* Increased padding for more "air" */
}
.bg-light { background-color: var(--light-grey); }

.section-title {
    text-align: center;
    margin-bottom: 60px; /* More space below title */
    font-size: 2.5rem;
    position: relative;
    display: inline-block; /* To make it fit content for centering trick */
    left: 50%;
    transform: translateX(-50%);
}
.section-title span {
    display: inline-block;
    padding-bottom: 10px;
    position: relative;
}
.section-title span::after { /* Underline effect */
    content: '';
    position: absolute;
    display: block;
    width: 70px;
    height: 4px;
    background: var(--gradient-blue);
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    border-radius: 2px;
}

/* --- About Section --- */
.about-grid {
    display: grid;
    grid-template-columns: 1fr 2fr; /* Image column, Text column */
    gap: 50px;
    align-items: center;
}
.about-image-container { text-align: center; }

.profile-photo {
    width: 300px;  /* Set a fixed width for the circular frame */
    height: 300px; /* Set a fixed height equal to the width */
    border-radius: 50%; /* This makes the element circular */
    object-fit: cover; /* Crucial: This scales the image to maintain aspect ratio while filling the element's content box. 
                          The image will be clipped to fit if its aspect ratio doesn't match the box. */
    border: 6px solid var(--beaver-blue);
    box-shadow: 0 10px 25px rgba(30, 64, 124, 0.2);
    display: block; /* Optional, but can help with layout consistency */
    margin-left: auto; /* Optional, if you want to center it within its container */
    margin-right: auto; /* Optional, if you want to center it within its container */
}


.about-text h3 { margin-bottom: 1rem; font-size: 1.75rem; }
.about-text p { color: var(--medium-grey); text-align: justify; }
.about-text strong { color: var(--beaver-blue); font-weight: 600; }

/* --- Experience Section (Timeline) --- */
.experience-timeline { position: relative; }
.experience-timeline::before { /* The central line */
    content: '';
    position: absolute;
    left: 20px; /* Adjust based on icon size */
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--light-grey); /* Match section bg or use accent */
    border-radius: 2px;
    background: #e0e6ed; /* A neutral line color */
}
.timeline-item {
    position: relative;
    margin-bottom: 50px;
    padding-left: 60px; /* Space for icon and line */
}
.timeline-item:last-child { margin-bottom: 0; }
.timeline-icon {
    position: absolute;
    left: 0;
    top: 0;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--gradient-blue);
    color: var(--white-out);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    box-shadow: 0 0 0 4px var(--white-out), inset 0 2px 0 rgba(0,0,0,0.08), 0 3px 0 4px rgba(0,0,0,0.05);
    transform: translateX(-50%); /* Center icon on the line */
    left: 22px; /* (line left + line width/2) */
}
.timeline-content {
    background: var(--white-out);
    padding: 25px;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    position: relative; /* For potential triangle pointer */
}
.timeline-content h4 { margin-bottom: 0.5rem; }
.timeline-content .institution {
    font-style: italic;
    color: var(--medium-grey);
    margin-bottom: 1rem;
    font-size: 0.9rem;
}
.timeline-content ul { list-style: disc; padding-left: 20px; }
.timeline-content ul li { margin-bottom: 0.5rem; color: var(--medium-grey); }

/* --- Skills Section --- */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(270px, 1fr));
    gap: 30px;
}
.skill-card {
    background: var(--white-out);
    padding: 30px;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    text-align: center;
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
}
.skill-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 30px rgba(30, 64, 124, 0.15);
}
.skill-icon {
    font-size: 2.5rem;
    color: var(--beaver-blue);
    margin-bottom: 1rem;
    height: 60px; /* Ensure consistent height for icons */
    line-height: 60px;
}
.skill-card h3 { font-size: 1.3rem; margin-bottom: 1rem; }
.skill-card ul { list-style: none; padding: 0; }
.skill-card ul li {
    color: var(--medium-grey);
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

/* --- Publications Section --- */
.publications-list { list-style: none; padding: 0; }
.publications-list li {
    background: var(--white-out);
    padding: 20px;
    margin-bottom: 20px;
    border-radius: var(--border-radius);
    box-shadow: 0 3px 10px rgba(0,0,0,0.05);
    font-size: 0.95rem;
    line-height: 1.6;
}
.publications-list li strong { color: var(--beaver-blue); } /* Highlight name */
.publications-list li em { color: var(--medium-grey); font-style: italic; } /* Journal */
.pub-link {
    font-weight: 600;
    font-size: 0.9rem;
    margin-left: 10px;
    color: var(--accent-blue-light);
}
.pub-link:hover { text-decoration: underline; }
#publications-loading-message { text-align: center; color: var(--medium-grey); }
.text-link { font-weight: 600; }

/* --- Education Section --- */
.education-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
}
.education-item {
    background: var(--white-out);
    padding: 25px;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    display: flex;
    flex-direction: column; /* Align icon on top */
    align-items: center; /* Center content */
    text-align: center;
}
.education-icon {
    font-size: 2.5rem;
    color: var(--beaver-blue);
    margin-bottom: 1rem;
}
.education-item h3 { font-size: 1.3rem; margin-bottom: 0.5rem; }
.education-item .institution {
    font-style: italic;
    color: var(--medium-grey);
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}
.education-item p:last-child { margin-bottom: 0; }

/* --- Contact Section --- */
.contact-section { background: var(--gradient-blue); color: var(--white-out); }
.contact-section .section-title span { color: var(--white-out); }
.contact-section .section-title span::after { background: var(--white-out); }
.contact-subtitle {
    text-align: center;
    font-size: 1.1rem;
    margin-bottom: 40px;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
    color: rgba(255,255,255,0.9);
}
.contact-details {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
    text-align: center;
}
.contact-details p {
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
    color: var(--white-out);
    min-width: 280px; /* Ensure items don't get too squished */
}
.contact-details p i { margin-right: 10px; font-size: 1.2rem; }
.contact-details a { color: var(--white-out); font-weight: 600; }
.contact-details a:hover { text-decoration: underline; opacity: 0.8; }

/* --- Footer --- */
#footer {
    background-color: var(--dark-text); /* Dark footer for contrast */
    color: var(--light-grey);
    text-align: center;
    padding: 30px 0;
    font-size: 0.9rem;
}
#footer p { margin-bottom: 0.25rem; opacity: 0.8; }

/* --- Responsive Design --- */
@media (max-width: 992px) {
    .hero-content h1 { font-size: 2.8rem; }
    .hero-content .subtitle { font-size: 1.15rem; }
    .about-grid { grid-template-columns: 1fr; text-align: center; }
    .about-image-container { margin-bottom: 30px; }
    .profile-photo { max-width: 250px; }
}

@media (max-width: 768px) {
    html { font-size: 15px; }
    .section-title { font-size: 2rem; }
    .hero-content h1 { font-size: 2.2rem; }
    .hero-content .subtitle { font-size: 1rem; }

    #header { height: auto; min-height: var(--header-height); }
    .header-container { flex-direction: column; padding: 0.5rem 0; }
    #navbar { width: 100%; }
    #navbar ul {
        flex-direction: column;
        width: 100%;
        background-color: var(--white-out); /* Solid background for mobile menu */
        position: absolute;
        top: 100%; /* Position below header */
        left: 0;
        padding: 1rem 0;
        box-shadow: var(--box-shadow);
        max-height: 0; /* Collapsed by default */
        overflow: hidden;
        transition: max-height 0.4s ease-in-out;
    }
    #navbar.active ul { max-height: 500px; /* Or enough to show all items */ }
    #navbar ul li { margin: 0.75rem 0; text-align: center; width: 100%; }
    #navbar ul li a,
    #header:not(.scrolled) #navbar ul li a { /* Ensure mobile nav links are always dark */
        color: var(--beaver-blue);
        width: 100%;
        display: block;
        padding: 0.5rem 0;
    }
    #navbar ul li a:hover,
    #navbar ul li a.active {
        background-color: var(--light-grey);
        border-bottom-color: transparent; /* No underline for full-width items */
    }

    #mobile-menu-toggle {
        display: block;
        background: none;
        border: none;
        color: var(--beaver-blue); /* Default for scrolled header */
        font-size: 1.5rem;
        cursor: pointer;
        position: absolute; /* Position relative to header */
        top: 50%;
        right: 1rem; /* Or align with container padding */
        transform: translateY(-50%);
    }
     #header:not(.scrolled) #mobile-menu-toggle { color: var(--white-out); }


    .experience-timeline::before { left: 20px; }
    .timeline-item { padding-left: 50px; }
    .timeline-icon { left: 20px; /* Adjust for mobile view if needed */ }
}

@media (max-width: 576px) {
    .hero-content h1 { font-size: 1.8rem; }
    .skills-grid { grid-template-columns: 1fr; }
    .education-grid { grid-template-columns: 1fr; }
}