/* ============================================
   JAVA BY JAY DADA — DESIGN SYSTEM
   Stripe / Vercel Inspired Premium Design
   ============================================ */

/* ─── CSS CUSTOM PROPERTIES ─── */
:root {
    /* Typography */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

    /* Sizing */
    --container-max: 1200px;
    --nav-height: 72px;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;

    /* Transitions */
    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-in-out: cubic-bezier(0.65, 0, 0.35, 1);
    --duration-fast: 150ms;
    --duration-normal: 300ms;
    --duration-slow: 500ms;
}

/* ─── DARK THEME (default) ─── */
[data-theme="dark"] {
    --bg-primary: #050816;
    --bg-secondary: #0a0e27;
    --bg-tertiary: #111338;
    --bg-card: rgba(17, 19, 56, 0.6);
    --bg-card-hover: rgba(24, 27, 75, 0.8);
    --bg-nav: rgba(5, 8, 22, 0.85);

    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-tertiary: #64748b;
    --text-inverse: #050816;

    --accent-blue: #3b82f6;
    --accent-purple: #8b5cf6;
    --accent-cyan: #06b6d4;
    --accent-green: #10b981;

    --border-color: rgba(148, 163, 184, 0.1);
    --border-color-hover: rgba(148, 163, 184, 0.2);

    --gradient-primary: linear-gradient(135deg, #3b82f6, #8b5cf6);
    --gradient-bg: linear-gradient(135deg, #050816 0%, #0a0e27 50%, #111338 100%);
    --gradient-card: linear-gradient(135deg, rgba(59, 130, 246, 0.1), rgba(139, 92, 246, 0.05));

    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 14px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 60px rgba(59, 130, 246, 0.15);
}

/* ─── LIGHT THEME ─── */
[data-theme="light"] {
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --bg-card: rgba(255, 255, 255, 0.8);
    --bg-card-hover: rgba(248, 250, 252, 1);
    --bg-nav: rgba(255, 255, 255, 0.9);

    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #94a3b8;
    --text-inverse: #ffffff;

    --accent-blue: #2563eb;
    --accent-purple: #7c3aed;
    --accent-cyan: #0891b2;
    --accent-green: #059669;

    --border-color: rgba(15, 23, 42, 0.08);
    --border-color-hover: rgba(15, 23, 42, 0.15);

    --gradient-primary: linear-gradient(135deg, #2563eb, #7c3aed);
    --gradient-bg: linear-gradient(135deg, #ffffff 0%, #f8fafc 50%, #f1f5f9 100%);
    --gradient-card: linear-gradient(135deg, rgba(37, 99, 235, 0.05), rgba(124, 58, 237, 0.03));

    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 14px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.1);
    --shadow-glow: 0 0 60px rgba(37, 99, 235, 0.08);
}

/* ─── RESET & BASE ─── */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--nav-height);
}

body {
    font-family: var(--font-primary);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
    transition: background-color var(--duration-slow) var(--ease-out),
                color var(--duration-slow) var(--ease-out);
}

a {
    color: inherit;
    text-decoration: none;
}

img {
    max-width: 100%;
    display: block;
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

ul {
    list-style: none;
}

/* ─── LAYOUT ─── */
.container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 24px;
}

.section {
    padding: 120px 0;
    position: relative;
}

.section-header {
    text-align: center;
    margin-bottom: 64px;
}

.section-tag {
    display: inline-block;
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.15em;
    color: var(--accent-blue);
    background: rgba(59, 130, 246, 0.1);
    padding: 6px 16px;
    border-radius: var(--radius-full);
    margin-bottom: 16px;
}

.section-title {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 16px;
    letter-spacing: -0.02em;
}

.section-desc {
    font-size: 1.1rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

.gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* ─── NAVIGATION ─── */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    height: var(--nav-height);
    display: flex;
    align-items: center;
    background: var(--bg-nav);
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    border-bottom: 1px solid var(--border-color);
    transition: all var(--duration-normal) var(--ease-out);
}

.navbar.scrolled {
    box-shadow: var(--shadow-md);
}

.nav-container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 24px;
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 700;
    font-size: 1.1rem;
    z-index: 1001;
}

.logo-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 38px;
    height: 38px;
    background: var(--gradient-primary);
    color: white;
    font-weight: 800;
    font-size: 0.85rem;
    border-radius: var(--radius-sm);
    letter-spacing: 0.03em;
}

.logo-text {
    color: var(--text-primary);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 4px;
}

.nav-link {
    padding: 8px 16px;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    transition: all var(--duration-fast) var(--ease-out);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--text-primary);
    background: rgba(59, 130, 246, 0.08);
}

.nav-link--cta {
    background: var(--gradient-primary) !important;
    color: white !important;
    margin-left: 8px;
    border-radius: var(--radius-full);
    padding: 8px 20px;
}

.nav-link--cta:hover {
    opacity: 0.9;
    transform: translateY(-1px);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 8px;
    z-index: 1001;
}

/* Theme Toggle */
.theme-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    transition: all var(--duration-fast) var(--ease-out);
}

.theme-toggle:hover {
    background: rgba(59, 130, 246, 0.08);
    color: var(--text-primary);
}

[data-theme="dark"] .theme-icon--moon { display: none; }
[data-theme="dark"] .theme-icon--sun  { display: block; }
[data-theme="light"] .theme-icon--sun  { display: none; }
[data-theme="light"] .theme-icon--moon { display: block; }

/* Hamburger */
.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    width: 40px;
    height: 40px;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    transition: all var(--duration-fast) var(--ease-out);
}

.hamburger:hover {
    background: rgba(59, 130, 246, 0.08);
}

.hamburger span {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--text-secondary);
    border-radius: 2px;
    transition: all var(--duration-normal) var(--ease-out);
}

.hamburger.active span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}

.hamburger.active span:nth-child(2) {
    opacity: 0;
}

.hamburger.active span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* ─── BUTTONS ─── */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 28px;
    font-size: 0.95rem;
    font-weight: 600;
    border-radius: var(--radius-full);
    transition: all var(--duration-normal) var(--ease-out);
    border: none;
    cursor: pointer;
    white-space: nowrap;
}

.btn--primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 4px 20px rgba(59, 130, 246, 0.3);
}

.btn--primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 30px rgba(59, 130, 246, 0.4);
}

.btn--secondary {
    background: var(--bg-card);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    backdrop-filter: blur(10px);
}

.btn--secondary:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-color-hover);
    transform: translateY(-2px);
}

.btn--ghost {
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
}

.btn--ghost:hover {
    color: var(--text-primary);
    border-color: var(--border-color-hover);
    background: rgba(59, 130, 246, 0.05);
    transform: translateY(-2px);
}

.btn--full {
    width: 100%;
    justify-content: center;
}

/* ─── HERO SECTION ─── */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    padding-top: var(--nav-height);
}

.hero-bg {
    position: absolute;
    inset: 0;
    z-index: 0;
}

.hero-gradient {
    position: absolute;
    inset: 0;
    background: var(--gradient-bg);
}

.hero-grid {
    position: absolute;
    inset: 0;
    background-image:
        linear-gradient(var(--border-color) 1px, transparent 1px),
        linear-gradient(90deg, var(--border-color) 1px, transparent 1px);
    background-size: 60px 60px;
    mask-image: radial-gradient(ellipse 80% 60% at 50% 40%, black 30%, transparent 100%);
    -webkit-mask-image: radial-gradient(ellipse 80% 60% at 50% 40%, black 30%, transparent 100%);
}

.hero-glow {
    position: absolute;
    border-radius: 50%;
    filter: blur(120px);
    opacity: 0.4;
    animation: float 8s ease-in-out infinite;
}

.hero-glow--1 {
    width: 600px;
    height: 600px;
    background: var(--accent-blue);
    top: -200px;
    right: -100px;
    opacity: 0.15;
}

.hero-glow--2 {
    width: 500px;
    height: 500px;
    background: var(--accent-purple);
    bottom: -150px;
    left: -100px;
    opacity: 0.1;
    animation-delay: -4s;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    33% { transform: translate(30px, -30px) scale(1.05); }
    66% { transform: translate(-20px, 20px) scale(0.95); }
}

.hero-content {
    position: relative;
    z-index: 1;
    text-align: center;
    padding: 60px 0;
}

.hero-badges {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 8px;
    margin-bottom: 32px;
}

.badge {
    display: inline-flex;
    align-items: center;
    padding: 6px 16px;
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--accent-blue);
    background: rgba(59, 130, 246, 0.08);
    border: 1px solid rgba(59, 130, 246, 0.15);
    border-radius: var(--radius-full);
    letter-spacing: 0.02em;
}

.hero-title {
    font-size: clamp(2.8rem, 7vw, 5rem);
    font-weight: 900;
    line-height: 1.1;
    letter-spacing: -0.03em;
    margin-bottom: 20px;
}

.hero-subtitle {
    font-size: clamp(1.05rem, 2vw, 1.3rem);
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 40px;
    line-height: 1.6;
}

.hero-cta {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 12px;
    margin-bottom: 64px;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 48px;
    flex-wrap: wrap;
}

.stat {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 2rem;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-tertiary);
    font-weight: 500;
}

.hero-scroll {
    position: absolute;
    bottom: 32px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 1;
}

.scroll-indicator {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    color: var(--text-tertiary);
    animation: bounce 2s ease-in-out infinite;
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(8px); }
}

/* ─── ABOUT SECTION ─── */
.about-grid {
    display: grid;
    grid-template-columns: 1.3fr 1fr;
    gap: 64px;
    align-items: start;
}

.about-intro {
    font-size: 1.2rem;
    line-height: 1.7;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.about-text p {
    color: var(--text-secondary);
    margin-bottom: 16px;
    line-height: 1.8;
}

.about-text strong {
    color: var(--text-primary);
    font-weight: 600;
}

.about-highlights {
    margin-top: 32px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.highlight-item {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 16px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    transition: all var(--duration-normal) var(--ease-out);
}

.highlight-item:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-color-hover);
    transform: translateX(4px);
}

.highlight-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    background: rgba(59, 130, 246, 0.1);
    border-radius: var(--radius-sm);
    color: var(--accent-blue);
    flex-shrink: 0;
}

.highlight-item strong {
    display: block;
    font-size: 0.95rem;
    color: var(--text-primary);
    margin-bottom: 2px;
}

.highlight-item span {
    font-size: 0.85rem;
    color: var(--text-tertiary);
}

/* Tech Stack */
.about-tech {
    position: sticky;
    top: calc(var(--nav-height) + 24px);
}

.tech-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 20px;
}

.tech-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.tech-pill {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-full);
    transition: all var(--duration-normal) var(--ease-out);
}

.tech-pill:hover {
    border-color: var(--border-color-hover);
    color: var(--text-primary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.tech-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--dot-color);
}

/* ─── COURSES SECTION ─── */
.courses {
    background: var(--bg-secondary);
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 32px;
}

.course-card {
    position: relative;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 40px;
    transition: all var(--duration-normal) var(--ease-out);
    overflow: hidden;
}

.course-card:hover {
    border-color: var(--border-color-hover);
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.course-card__glow {
    position: absolute;
    top: -100px;
    right: -100px;
    width: 250px;
    height: 250px;
    background: var(--gradient-primary);
    border-radius: 50%;
    filter: blur(100px);
    opacity: 0.06;
    transition: opacity var(--duration-slow) var(--ease-out);
}

.course-card:hover .course-card__glow {
    opacity: 0.12;
}

.course-card__badge {
    position: absolute;
    top: 20px;
    right: 20px;
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    padding: 4px 12px;
    background: var(--gradient-primary);
    color: white;
    border-radius: var(--radius-full);
}

.course-card__icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 64px;
    height: 64px;
    background: rgba(59, 130, 246, 0.1);
    border-radius: var(--radius-md);
    color: var(--accent-blue);
    margin-bottom: 24px;
}

.course-card__title {
    font-size: 1.4rem;
    font-weight: 700;
    margin-bottom: 12px;
    letter-spacing: -0.01em;
}

.course-card__desc {
    font-size: 0.95rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 20px;
}

.course-card__topics {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 20px;
}

.topic-pill {
    font-size: 0.78rem;
    font-weight: 500;
    padding: 5px 12px;
    background: rgba(59, 130, 246, 0.08);
    color: var(--accent-blue);
    border-radius: var(--radius-full);
    border: 1px solid rgba(59, 130, 246, 0.12);
}

.course-card__meta {
    display: flex;
    gap: 16px;
    font-size: 0.85rem;
    color: var(--text-tertiary);
    margin-bottom: 24px;
    padding-top: 16px;
    border-top: 1px solid var(--border-color);
}

/* ─── PROJECTS SECTION ─── */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}

.project-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 32px;
    transition: all var(--duration-normal) var(--ease-out);
    display: flex;
    flex-direction: column;
}

.project-card:hover {
    border-color: var(--border-color-hover);
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.project-card__header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
    color: var(--accent-blue);
}

.project-card__links {
    display: flex;
    gap: 8px;
}

.project-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    color: var(--text-tertiary);
    transition: all var(--duration-fast) var(--ease-out);
}

.project-link:hover {
    color: var(--text-primary);
    background: rgba(59, 130, 246, 0.08);
}

.project-card__title {
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 10px;
}

.project-card__desc {
    font-size: 0.92rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 20px;
    flex-grow: 1;
}

.project-card__tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.project-card__tags span {
    font-size: 0.78rem;
    font-weight: 500;
    padding: 4px 10px;
    color: var(--text-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-full);
}

/* ─── RESEARCH SECTION ─── */
.research {
    background: var(--bg-secondary);
}

.research-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.research-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 32px;
    transition: all var(--duration-normal) var(--ease-out);
    display: flex;
    flex-direction: column;
}

.research-card:hover {
    border-color: var(--border-color-hover);
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.research-card__category {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent-purple);
    margin-bottom: 16px;
}

.research-card__title {
    font-size: 1.15rem;
    font-weight: 700;
    margin-bottom: 12px;
    line-height: 1.3;
}

.research-card__desc {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.7;
    flex-grow: 1;
    margin-bottom: 20px;
}

.research-card__footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: 16px;
    border-top: 1px solid var(--border-color);
}

.research-card__date {
    font-size: 0.85rem;
    color: var(--text-tertiary);
}

.research-card__link {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--accent-blue);
    transition: color var(--duration-fast) var(--ease-out);
}

.research-card__link:hover {
    color: var(--accent-purple);
}

/* ─── PRESENTATIONS SECTION ─── */
.talks-grid {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.talk-card {
    display: flex;
    gap: 32px;
    align-items: flex-start;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 32px;
    transition: all var(--duration-normal) var(--ease-out);
}

.talk-card:hover {
    border-color: var(--border-color-hover);
    transform: translateX(4px);
    box-shadow: var(--shadow-md);
}

.talk-card__number {
    font-size: 3rem;
    font-weight: 900;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
    flex-shrink: 0;
    opacity: 0.4;
}

.talk-card__meta {
    display: flex;
    gap: 12px;
    margin-bottom: 8px;
}

.talk-card__type {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--accent-cyan);
    background: rgba(6, 182, 212, 0.1);
    padding: 3px 10px;
    border-radius: var(--radius-full);
}

.talk-card__year {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-tertiary);
    padding: 3px 0;
}

.talk-card__title {
    font-size: 1.15rem;
    font-weight: 700;
    margin-bottom: 8px;
}

.talk-card__desc {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 12px;
}

.talk-card__tags {
    display: flex;
    gap: 8px;
}

.talk-card__tags span {
    font-size: 0.75rem;
    font-weight: 500;
    padding: 3px 10px;
    color: var(--text-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-full);
}

/* ─── BLOG SECTION ─── */
.blog {
    background: var(--bg-secondary);
}

.blog-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.blog-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: all var(--duration-normal) var(--ease-out);
}

.blog-card:hover {
    border-color: var(--border-color-hover);
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.blog-card__image {
    height: 180px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--accent, #3b82f6), rgba(139, 92, 246, 0.6));
    position: relative;
    overflow: hidden;
}

.blog-card__image::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(to bottom, transparent 50%, var(--bg-card) 100%);
}

.blog-card__icon {
    font-size: 3rem;
    z-index: 1;
    filter: drop-shadow(0 4px 8px rgba(0, 0, 0, 0.2));
}

.blog-card__body {
    padding: 24px;
}

.blog-card__meta {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 12px;
}

.blog-card__tag {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--accent-blue);
    background: rgba(59, 130, 246, 0.1);
    padding: 3px 10px;
    border-radius: var(--radius-full);
}

.blog-card__date {
    font-size: 0.8rem;
    color: var(--text-tertiary);
}

.blog-card__title {
    font-size: 1.1rem;
    font-weight: 700;
    margin-bottom: 8px;
    line-height: 1.3;
}

.blog-card__excerpt {
    font-size: 0.88rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 16px;
}

.blog-card__read {
    font-size: 0.88rem;
    font-weight: 600;
    color: var(--accent-blue);
    transition: color var(--duration-fast) var(--ease-out);
}

.blog-card__read:hover {
    color: var(--accent-purple);
}

/* ─── CONTACT SECTION ─── */
.contact-grid {
    display: grid;
    grid-template-columns: 1.2fr 1fr;
    gap: 48px;
    align-items: start;
}

.contact-form {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.form-group label {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 14px 18px;
    font-family: var(--font-primary);
    font-size: 0.95rem;
    color: var(--text-primary);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    outline: none;
    transition: all var(--duration-fast) var(--ease-out);
}

.form-group input:focus,
.form-group textarea:focus {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.15);
}

.form-group input::placeholder,
.form-group textarea::placeholder {
    color: var(--text-tertiary);
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

.contact-info__card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 32px;
}

.contact-info__card h3 {
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 8px;
}

.contact-info__card > p {
    font-size: 0.92rem;
    color: var(--text-secondary);
    margin-bottom: 24px;
    line-height: 1.7;
}

.contact-links {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.contact-link {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 16px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    transition: all var(--duration-normal) var(--ease-out);
}

.contact-link:hover {
    background: rgba(59, 130, 246, 0.05);
    border-color: var(--border-color-hover);
    transform: translateX(4px);
}

.contact-link__icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    border-radius: var(--radius-sm);
    background: rgba(59, 130, 246, 0.1);
    color: var(--accent-blue);
    flex-shrink: 0;
}

.contact-link strong {
    display: block;
    font-size: 0.95rem;
    color: var(--text-primary);
    margin-bottom: 2px;
}

.contact-link span {
    font-size: 0.82rem;
    color: var(--text-tertiary);
}

/* ─── FOOTER ─── */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: 64px 0 32px;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    margin-bottom: 48px;
}

.footer-brand {
    max-width: 320px;
}

.footer-brand .nav-logo {
    margin-bottom: 12px;
}

.footer-brand p {
    font-size: 0.9rem;
    color: var(--text-tertiary);
    line-height: 1.7;
}

.footer-links {
    display: flex;
    gap: 64px;
}

.footer-col h4 {
    font-size: 0.85rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-primary);
    margin-bottom: 16px;
}

.footer-col a {
    display: block;
    font-size: 0.9rem;
    color: var(--text-tertiary);
    margin-bottom: 10px;
    transition: color var(--duration-fast) var(--ease-out);
}

.footer-col a:hover {
    color: var(--accent-blue);
}

.footer-bottom {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: 24px;
    border-top: 1px solid var(--border-color);
    font-size: 0.85rem;
    color: var(--text-tertiary);
}

/* ─── SCROLL ANIMATIONS ─── */
.animate-in {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s var(--ease-out), transform 0.8s var(--ease-out);
}

.animate-in.visible {
    opacity: 1;
    transform: translateY(0);
}

.animate-in:nth-child(2) { transition-delay: 0.1s; }
.animate-in:nth-child(3) { transition-delay: 0.2s; }
.animate-in:nth-child(4) { transition-delay: 0.3s; }

/* ─── RESPONSIVE ─── */
@media (max-width: 1024px) {
    .about-grid {
        grid-template-columns: 1fr;
        gap: 48px;
    }

    .about-tech {
        position: static;
    }

    .courses-grid {
        grid-template-columns: 1fr;
    }

    .research-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .blog-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .contact-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .section {
        padding: 80px 0;
    }

    .section-header {
        margin-bottom: 40px;
    }

    /* Mobile Nav */
    .nav-links {
        position: fixed;
        top: 0;
        right: -100%;
        width: 80%;
        max-width: 360px;
        height: 100vh;
        background: var(--bg-primary);
        border-left: 1px solid var(--border-color);
        flex-direction: column;
        align-items: flex-start;
        padding: calc(var(--nav-height) + 24px) 32px 32px;
        gap: 4px;
        transition: right var(--duration-normal) var(--ease-out);
        z-index: 999;
    }

    .nav-links.open {
        right: 0;
    }

    .nav-link {
        font-size: 1rem;
        padding: 12px 16px;
        width: 100%;
    }

    .nav-link--cta {
        margin-left: 0;
        margin-top: 8px;
        text-align: center;
        justify-content: center;
        display: flex;
    }

    .hamburger {
        display: flex;
    }

    /* Hero Mobile */
    .hero-title {
        font-size: clamp(2.2rem, 8vw, 3.5rem);
    }

    .hero-cta {
        flex-direction: column;
        align-items: stretch;
        max-width: 300px;
        margin-left: auto;
        margin-right: auto;
    }

    .hero-cta .btn {
        justify-content: center;
    }

    .hero-stats {
        gap: 24px;
    }

    .stat-number {
        font-size: 1.5rem;
    }

    /* Projects Mobile */
    .projects-grid {
        grid-template-columns: 1fr;
    }

    /* Research & Blog Mobile */
    .research-grid,
    .blog-grid {
        grid-template-columns: 1fr;
    }

    /* Talks Mobile */
    .talk-card {
        flex-direction: column;
        gap: 16px;
    }

    .talk-card__number {
        font-size: 2rem;
    }

    /* Footer Mobile */
    .footer-content {
        flex-direction: column;
        gap: 32px;
    }

    .footer-links {
        gap: 32px;
    }

    .footer-bottom {
        flex-direction: column;
        gap: 8px;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }

    .hero-badges {
        gap: 6px;
    }

    .badge {
        font-size: 0.72rem;
        padding: 4px 12px;
    }

    .course-card {
        padding: 24px;
    }

    .hero-stats {
        gap: 16px;
    }

    .stat-number {
        font-size: 1.3rem;
    }

    .stat-label {
        font-size: 0.75rem;
    }
}

/* ─── MOBILE OVERLAY ─── */
.mobile-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    z-index: 998;
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--duration-normal) var(--ease-out);
}

.mobile-overlay.active {
    opacity: 1;
    pointer-events: auto;
}

/* ─── FORM SUCCESS STATE ─── */
.form-success {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 48px;
    text-align: center;
    gap: 16px;
}

.form-success svg {
    color: var(--accent-green);
}

.form-success h3 {
    font-size: 1.3rem;
    font-weight: 700;
}

.form-success p {
    color: var(--text-secondary);
}