/* ============================================================
   SAHIL GOYAL — Portfolio Design System
   Premium Light-Mode Academic Portfolio
   ============================================================ */

/* --- Google Fonts (Inter 300/400/600/700) --- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;600;700&display=swap');

/* --- CSS Custom Properties --- */
:root {
    --color-bg: #f8fafc;
    --color-bg-alt: #ffffff;
    --color-text: #1e293b;
    --color-text-muted: #64748b;
    --color-text-light: #94a3b8;
    --color-accent: #6366f1;
    --color-accent-secondary: #06b6d4;
    --color-border: #e2e8f0;
    --color-border-hover: #cbd5e1;
    --color-card-bg: #ffffff;
    --color-sidebar-bg: #ffffff;
    --gradient-accent: linear-gradient(135deg, #6366f1, #06b6d4);
    --gradient-accent-soft: linear-gradient(135deg, rgba(99,102,241,0.08), rgba(6,182,212,0.08));
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.06);
    --shadow-lg: 0 8px 32px rgba(0,0,0,0.08);
    --shadow-glow: 0 0 20px rgba(99,102,241,0.15);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --sidebar-width: 220px;
    --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-smooth: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* --- Reset & Base --- */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.7;
    display: flex;
    min-height: 100vh;
}

a {
    color: var(--color-accent);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--color-accent-secondary);
}

img {
    max-width: 100%;
    height: auto;
}

/* --- Keyframe Animations --- */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(24px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes pulseGlow {
    0%, 100% { box-shadow: 0 0 0 0 rgba(99,102,241,0.3); }
    50% { box-shadow: 0 0 0 8px rgba(99,102,241,0); }
}

@keyframes shimmer {
    0% { background-position: -200% 0; }
    100% { background-position: 200% 0; }
}

/* --- Sidebar Navigation --- */
.sidenav {
    width: var(--sidebar-width);
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    background: var(--color-sidebar-bg);
    border-right: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
    z-index: 100;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.navblock {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
}

.navblock_text {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 100%;
    padding: 20px 0;
    gap: 4px;
}

.sidenav a {
    padding: 12px 20px;
    text-decoration: none;
    font-size: 15px;
    font-weight: 600;
    letter-spacing: 0.02em;
    color: var(--color-text-muted);
    display: block;
    width: 80%;
    text-align: center;
    border-radius: var(--radius-sm);
    transition: all var(--transition-smooth);
    position: relative;
}

.sidenav a:hover {
    color: var(--color-accent);
    background: var(--gradient-accent-soft);
    transform: translateX(3px);
}

.sidenav a.active {
    color: var(--color-accent);
    font-weight: 700;
    background: var(--gradient-accent-soft);
}

.sidenav a.active::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 3px;
    height: 60%;
    background: var(--gradient-accent);
    border-radius: 0 4px 4px 0;
}

/* --- Main Content Area --- */
.main-content {
    margin-left: var(--sidebar-width);
    padding: 50px 60px;
    width: 100%;
    min-height: 100vh;
    animation: fadeIn 0.5s ease;
}

/* --- Page Headers --- */
.page-header {
    margin-bottom: 40px;
}

.page-header h2, h2 {
    font-size: 2em;
    font-weight: 700;
    color: var(--color-text);
    position: relative;
    padding-bottom: 12px;
    margin-bottom: 20px;
}

.page-header h2::after, h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 60px;
    height: 3px;
    background: var(--gradient-accent);
    border-radius: 2px;
}

h3 {
    font-size: 1.5em;
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--color-border);
}

/* ============================================================
   INDEX / ABOUT PAGE
   ============================================================ */
.about-container {
    display: flex;
    align-items: center;
    gap: 50px;
    max-width: 900px;
    animation: fadeInUp 0.6s ease both;
}

.about-photo-wrapper {
    flex-shrink: 0;
}

.about-photo {
    width: 200px;
    height: 200px;
    border-radius: 50%;
    object-fit: cover;
    border: 4px solid transparent;
    background-image: var(--gradient-accent);
    background-origin: border-box;
    background-clip: content-box, border-box;
    box-shadow: var(--shadow-lg);
    transition: transform var(--transition-smooth), box-shadow var(--transition-smooth);
    animation: pulseGlow 3s ease-in-out infinite;
}

.about-photo:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-glow);
}

.about-text {
    animation: fadeInUp 0.6s ease 0.15s both;
}

.about-text h1 {
    font-size: 2.5em;
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: 8px;
    letter-spacing: -0.02em;
}

.about-text .tagline {
    font-size: 1.1em;
    font-weight: 400;
    color: var(--color-text-muted);
    margin-bottom: 16px;
}

.about-text p {
    font-size: 1.05em;
    line-height: 1.8;
    color: var(--color-text);
    margin-bottom: 20px;
}

.email-info {
    font-family: 'Inter', monospace;
    background: var(--gradient-accent-soft);
    padding: 14px 20px;
    border-radius: var(--radius-sm);
    font-size: 0.88em;
    color: var(--color-text-muted);
    text-align: center;
    line-height: 1.8;
    border: 1px solid var(--color-border);
    margin: 20px 0;
    animation: fadeInUp 0.6s ease 0.3s both;
}

/* --- Social Links --- */
.about_links {
    margin-top: 25px;
    display: flex;
    gap: 20px;
    align-items: center;
    animation: fadeInUp 0.6s ease 0.4s both;
}

.about_links a {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    color: var(--color-text-muted);
    border: 1.5px solid var(--color-border);
    transition: all var(--transition-smooth);
}

.about_links a:hover {
    color: #fff;
    background: var(--gradient-accent);
    border-color: transparent;
    transform: translateY(-3px);
    box-shadow: var(--shadow-glow);
}

.about_links a svg {
    width: 20px;
    height: 20px;
    fill: currentColor;
}

/* ============================================================
   RESEARCH PAGE
   ============================================================ */
.research-container {
    max-width: 900px;
}

.research-container > p {
    font-size: 1.05em;
    line-height: 1.8;
    color: var(--color-text);
    margin-bottom: 24px;
    animation: fadeInUp 0.5s ease both;
}

/* --- Publication Items --- */
.publication-item {
    display: flex;
    gap: 28px;
    align-items: flex-start;
    padding: 24px;
    margin-bottom: 24px;
    background: var(--color-card-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-smooth);
    animation: fadeInUp 0.5s ease both;
}

.publication-item:nth-child(1) { animation-delay: 0.1s; }
.publication-item:nth-child(2) { animation-delay: 0.15s; }
.publication-item:nth-child(3) { animation-delay: 0.2s; }
.publication-item:nth-child(4) { animation-delay: 0.25s; }

.publication-item:hover {
    border-color: var(--color-accent);
    box-shadow: var(--shadow-md), 0 0 0 1px rgba(99,102,241,0.1);
    transform: translateY(-2px);
}

.publication-image {
    flex-shrink: 0;
    width: 200px;
    height: auto;
    border-radius: var(--radius-sm);
    border: 1px solid var(--color-border);
    transition: all var(--transition-smooth);
}

.publication-item:hover .publication-image {
    border-color: var(--color-accent);
    box-shadow: var(--shadow-sm);
}

.publication-details h4 {
    margin: 0 0 8px 0;
    font-size: 1.15em;
    font-weight: 700;
    color: var(--color-text);
    line-height: 1.4;
}

.publication-details p {
    margin: 0 0 14px 0;
    line-height: 1.6;
    font-size: 0.95em;
    color: var(--color-text-muted);
}

.publication-links {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.publication-links a {
    display: inline-block;
    padding: 5px 14px;
    font-size: 0.82em;
    font-weight: 600;
    color: var(--color-accent);
    background: var(--gradient-accent-soft);
    border: 1px solid rgba(99,102,241,0.2);
    border-radius: 20px;
    transition: all var(--transition-smooth);
}

.publication-links a:hover {
    color: #fff;
    background: var(--gradient-accent);
    border-color: transparent;
    transform: translateY(-1px);
    box-shadow: 0 2px 8px rgba(99,102,241,0.3);
}

/* ============================================================
   BLOG PAGE
   ============================================================ */
.blog-container {
    max-width: 900px;
}

.blog-container > p {
    font-size: 1.05em;
    line-height: 1.8;
    color: var(--color-text);
    margin-bottom: 30px;
    animation: fadeInUp 0.5s ease both;
}

/* --- Blog Post Cards --- */
.blog-post {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 22px 28px;
    margin-bottom: 14px;
    background: var(--color-card-bg);
    border: 1px solid var(--color-border);
    border-left: 4px solid transparent;
    border-image: var(--gradient-accent) 1;
    border-image-slice: 0 0 0 1;
    border-radius: var(--radius-md);
    text-decoration: none;
    color: var(--color-text);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-smooth);
    animation: fadeInUp 0.5s ease both;
    overflow: hidden;
}

.blog-post:nth-child(2) { animation-delay: 0.05s; }
.blog-post:nth-child(3) { animation-delay: 0.1s; }
.blog-post:nth-child(4) { animation-delay: 0.15s; }
.blog-post:nth-child(5) { animation-delay: 0.2s; }

.blog-post:hover {
    border-image-slice: 0 0 0 4;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.blog-post h3 {
    margin: 0 0 6px 0;
    font-size: 1.15em;
    font-weight: 600;
    color: var(--color-text);
    border: none;
    padding: 0;
}

.blog-post .blog-date {
    font-size: 0.85em;
    color: var(--color-text-light);
    margin: 0;
}

.blog-icon svg {
    width: 22px;
    height: 22px;
    color: var(--color-text-light);
    transition: all var(--transition-smooth);
}

.blog-post:hover .blog-icon svg {
    color: var(--color-accent);
    transform: translateX(4px) translateY(-4px);
}

/* ============================================================
   NEWS PAGE
   ============================================================ */
.news-container {
    max-width: 900px;
}

/* --- News Timeline --- */
.news-timeline {
    list-style: none;
    padding: 0;
    position: relative;
    margin-top: 10px;
}

.news-timeline::before {
    content: '';
    position: absolute;
    top: 8px;
    left: 6px;
    height: calc(100% - 16px);
    width: 2px;
    background: linear-gradient(to bottom, var(--color-accent), var(--color-accent-secondary), transparent);
    border-radius: 2px;
}

.news-timeline li {
    margin-bottom: 22px;
    padding-left: 32px;
    position: relative;
    line-height: 1.7;
    font-size: 0.98em;
    animation: fadeInUp 0.4s ease both;
}

.news-timeline li:nth-child(1) { animation-delay: 0.05s; }
.news-timeline li:nth-child(2) { animation-delay: 0.1s; }
.news-timeline li:nth-child(3) { animation-delay: 0.15s; }
.news-timeline li:nth-child(4) { animation-delay: 0.2s; }
.news-timeline li:nth-child(5) { animation-delay: 0.25s; }
.news-timeline li:nth-child(6) { animation-delay: 0.3s; }
.news-timeline li:nth-child(7) { animation-delay: 0.35s; }
.news-timeline li:nth-child(8) { animation-delay: 0.4s; }
.news-timeline li:nth-child(9) { animation-delay: 0.45s; }
.news-timeline li:nth-child(10) { animation-delay: 0.5s; }
.news-timeline li:nth-child(n+11) { animation-delay: 0.55s; }

.news-timeline li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 8px;
    width: 14px;
    height: 14px;
    border-radius: 50%;
    background: var(--gradient-accent);
    border: 3px solid var(--color-bg);
    box-shadow: 0 0 0 2px var(--color-accent);
    z-index: 1;
    transition: transform var(--transition-fast);
}

.news-timeline li:hover::before {
    transform: scale(1.3);
}

.news-timeline .date {
    font-weight: 700;
    color: var(--color-accent);
    margin-right: 10px;
    font-size: 0.9em;
}

.news-timeline a {
    color: var(--color-accent);
    font-weight: 600;
}

.news-timeline a:hover {
    text-decoration: underline;
}

/* ============================================================
   RESUME PAGE
   ============================================================ */
.resume-container {
    max-width: 900px;
    margin: 0 auto;
}

.pdf-viewer {
    width: 100%;
    height: 82vh;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    animation: fadeInUp 0.5s ease 0.1s both;
}

.pdf-viewer p {
    background: var(--gradient-accent-soft);
    padding: 30px;
    border-radius: var(--radius-md);
    text-align: center;
    line-height: 1.7;
    color: var(--color-text-muted);
}

.pdf-viewer a {
    display: inline-block;
    padding: 10px 24px;
    margin-top: 12px;
    font-weight: 600;
    color: #fff;
    background: var(--gradient-accent);
    border-radius: 24px;
    transition: all var(--transition-smooth);
}

.pdf-viewer a:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(99,102,241,0.3);
    color: #fff;
}

/* ============================================================
   COLLABORATION PAGE
   ============================================================ */
.collaboration-container {
    max-width: 900px;
}

.collaboration-card {
    background: var(--color-card-bg);
    padding: 28px 30px;
    margin-bottom: 20px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-smooth);
    animation: fadeInUp 0.5s ease both;
}

.collaboration-card:nth-child(1) { animation-delay: 0.1s; }
.collaboration-card:nth-child(2) { animation-delay: 0.15s; }
.collaboration-card:nth-child(3) { animation-delay: 0.2s; }

.collaboration-card:hover {
    border-color: var(--color-accent);
    box-shadow: var(--shadow-md), 0 0 0 1px rgba(99,102,241,0.08);
    transform: translateY(-2px);
}

.collaboration-card h3 {
    margin: 0 0 4px 0;
    font-size: 1.35em;
    border: none;
    padding: 0;
}

.collaboration-card h3 a {
    color: var(--color-text);
    font-weight: 700;
    transition: color var(--transition-fast);
}

.collaboration-card h3 a:hover {
    color: var(--color-accent);
}

.collaboration-card .role {
    font-size: 1em;
    font-style: italic;
    color: var(--color-text-muted);
    margin: 0 0 20px 0;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--color-border);
}

.people-list h4 {
    margin: 0 0 8px 0;
    font-size: 0.85em;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--color-text-light);
}

.people-list p {
    margin: 0 0 14px 0;
    line-height: 1.7;
}

.people-list a {
    color: var(--color-accent);
    font-weight: 500;
}

.people-list a:hover {
    text-decoration: underline;
    color: var(--color-accent-secondary);
}

/* ============================================================
   RESPONSIVE DESIGN
   ============================================================ */
@media (max-width: 768px) {
    body {
        flex-direction: column;
    }

    .sidenav {
        position: relative;
        width: 100%;
        height: auto;
        border-right: none;
        border-bottom: 1px solid var(--color-border);
        box-shadow: var(--shadow-sm);
    }

    .navblock {
        align-items: stretch;
    }

    .navblock_text {
        flex-direction: row;
        justify-content: center;
        flex-wrap: wrap;
        padding: 12px 8px;
        gap: 0;
    }

    .sidenav a {
        width: auto;
        padding: 8px 14px;
        font-size: 13px;
    }

    .sidenav a:hover {
        transform: none;
    }

    .sidenav a.active::before {
        display: none;
    }

    .main-content {
        margin-left: 0;
        padding: 24px 20px;
    }

    /* About page */
    .about-container {
        flex-direction: column;
        text-align: center;
        gap: 30px;
    }

    .about_links {
        justify-content: center;
    }

    /* Research page */
    .publication-item {
        flex-direction: column;
        align-items: stretch;
    }

    .publication-image {
        width: 100%;
        max-width: 300px;
    }

    /* Resume page */
    .pdf-viewer {
        height: 70vh;
    }
}

@media (max-width: 480px) {
    .about-text h1 {
        font-size: 1.8em;
    }

    .about-photo {
        width: 150px;
        height: 150px;
    }

    .sidenav a {
        padding: 6px 10px;
        font-size: 12px;
    }
}