/* ===== RESET & BASE ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --teal-900: #0f4c47;
    --teal-800: #115e58;
    --teal-700: #14746b;
    --teal-600: #178d82;
    --teal-500: #1aa398;
    --teal-100: #d9f2f0;
    --teal-50: #effafa;
    --ink: #102a2a;
    --ink-soft: #3b5555;
    --muted: #6b8181;
    --line: #e2ecea;
    --white: #ffffff;
    --bg: #ffffff;
    --bg-alt: #f7fbfb;
    --shadow-sm: 0 1px 3px rgba(15, 76, 71, 0.08);
    --shadow-md: 0 8px 24px rgba(15, 76, 71, 0.08);
    --shadow-lg: 0 16px 48px rgba(15, 76, 71, 0.12);
    --radius: 14px;
    --radius-lg: 20px;
    --container: 1120px;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    color: var(--ink);
    background: var(--bg);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    overflow-x: hidden;
}

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

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

ul {
    list-style: none;
}

/* ===== NAVIGATION ===== */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid transparent;
    transition: background 0.3s ease, border-color 0.3s ease, box-shadow 0.3s ease;
}

.nav.scrolled {
    background: rgba(255, 255, 255, 0.97);
    border-bottom: 1px solid var(--line);
    box-shadow: var(--shadow-sm);
}

.nav-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.nav-logo {
    font-weight: 800;
    font-size: 1.3rem;
    color: var(--teal-700);
    letter-spacing: -0.02em;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 8px;
}

.nav-links a {
    padding: 8px 14px;
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--ink-soft);
    border-radius: 8px;
    transition: color 0.2s ease, background 0.2s ease;
}

.nav-links a:hover {
    color: var(--teal-700);
    background: var(--teal-50);
}

.nav-links .nav-cta {
    background: var(--teal-700);
    color: var(--white);
    padding: 8px 18px;
    border-radius: 8px;
    font-weight: 600;
}

.nav-links .nav-cta:hover {
    background: var(--teal-800);
    color: var(--white);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle span {
    width: 22px;
    height: 2px;
    background: var(--ink);
    border-radius: 2px;
    transition: transform 0.3s ease, opacity 0.3s ease;
}

.nav-toggle.active span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}
.nav-toggle.active span:nth-child(2) {
    opacity: 0;
}
.nav-toggle.active span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* ===== HERO ===== */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: 120px 0 80px;
    overflow: hidden;
    background: linear-gradient(180deg, #ffffff 0%, #f6fbfa 100%);
}

.hero-bg-grid {
    position: absolute;
    inset: 0;
    background-image:
        linear-gradient(rgba(23, 141, 130, 0.05) 1px, transparent 1px),
        linear-gradient(90deg, rgba(23, 141, 130, 0.05) 1px, transparent 1px);
    background-size: 56px 56px;
    mask-image: radial-gradient(circle at 50% 40%, black, transparent 80%);
    -webkit-mask-image: radial-gradient(circle at 50% 40%, black, transparent 80%);
    pointer-events: none;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 860px;
}

.hero-badge {
    display: inline-block;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--teal-700);
    background: var(--teal-50);
    border: 1px solid var(--teal-100);
    padding: 6px 14px;
    border-radius: 100px;
    margin-bottom: 28px;
    letter-spacing: 0.02em;
}

.hero-name {
    font-size: clamp(2.6rem, 7vw, 4.5rem);
    font-weight: 800;
    line-height: 1.05;
    letter-spacing: -0.03em;
    color: var(--ink);
    margin-bottom: 18px;
}

.hero-role {
    font-size: clamp(1.1rem, 2.5vw, 1.4rem);
    font-weight: 600;
    color: var(--teal-700);
    margin-bottom: 14px;
}

.hero-tagline {
    font-size: clamp(1rem, 2vw, 1.15rem);
    color: var(--ink-soft);
    max-width: 620px;
    margin-bottom: 40px;
}

.hero-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 16px;
    margin-bottom: 40px;
    max-width: 720px;
}

.stat-card {
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 20px 18px;
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.stat-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
}

.stat-number {
    display: block;
    font-size: 1.9rem;
    font-weight: 800;
    color: var(--teal-700);
    line-height: 1.1;
    margin-bottom: 4px;
}

.stat-label {
    font-size: 0.82rem;
    color: var(--muted);
    font-weight: 500;
}

.hero-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

/* ===== BUTTONS ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 24px;
    border-radius: 10px;
    font-size: 0.95rem;
    font-weight: 600;
    transition: all 0.2s ease;
    cursor: pointer;
    border: 1px solid transparent;
}

.btn-primary {
    background: var(--teal-700);
    color: var(--white);
}

.btn-primary:hover {
    background: var(--teal-800);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-outline {
    background: var(--white);
    border-color: var(--line);
    color: var(--ink);
}

.btn-outline:hover {
    border-color: var(--teal-500);
    color: var(--teal-700);
    background: var(--teal-50);
    transform: translateY(-1px);
}

.btn-sm {
    padding: 9px 18px;
    font-size: 0.88rem;
}

.btn-white {
    background: var(--white);
    color: var(--teal-800);
}

.btn-white:hover {
    background: var(--teal-50);
    transform: translateY(-1px);
    box-shadow: 0 8px 24px rgba(255, 255, 255, 0.3);
}

.btn-outline-light {
    background: transparent;
    border-color: rgba(255, 255, 255, 0.45);
    color: var(--white);
}

.btn-outline-light:hover {
    border-color: var(--white);
    background: rgba(255, 255, 255, 0.1);
}

/* ===== SECTIONS ===== */
.section {
    padding: 96px 0;
}

.section-alt {
    background: var(--bg-alt);
}

.section-header {
    max-width: 720px;
    margin-bottom: 56px;
}

.section-tag {
    display: inline-block;
    font-size: 0.8rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--teal-600);
    margin-bottom: 12px;
}

.section-tag-light {
    color: var(--teal-100);
}

.section-title {
    font-size: clamp(1.8rem, 4vw, 2.5rem);
    font-weight: 800;
    letter-spacing: -0.02em;
    color: var(--ink);
    margin-bottom: 12px;
}

.section-subtitle {
    font-size: 1.05rem;
    color: var(--muted);
}

/* ===== PROJECT CARDS ===== */
.project-card {
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    padding: 40px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-sm);
    transition: box-shadow 0.3s ease, transform 0.3s ease;
}

.project-card:hover {
    box-shadow: var(--shadow-md);
}

.project-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 12px;
    margin-bottom: 14px;
}

.project-meta {
    display: flex;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
}

.project-type {
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--teal-700);
    background: var(--teal-50);
    border: 1px solid var(--teal-100);
    padding: 4px 12px;
    border-radius: 100px;
}

.project-date {
    font-size: 0.85rem;
    color: var(--muted);
}

.project-company {
    font-size: 0.85rem;
    color: var(--teal-700);
    font-weight: 600;
    background: var(--teal-50);
    padding: 4px 12px;
    border-radius: 100px;
}

.project-name {
    font-size: clamp(1.6rem, 3vw, 2rem);
    font-weight: 800;
    letter-spacing: -0.02em;
    margin-bottom: 2px;
}

.project-subtitle {
    font-size: 1.05rem;
    color: var(--ink-soft);
    margin-bottom: 32px;
    font-weight: 500;
}

.project-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 28px;
    margin-bottom: 32px;
}

.project-block-full {
    grid-column: 1 / -1;
}

.problem-solution-list {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
}

.ps-item {
    background: var(--bg-alt);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 20px;
}

.ps-heading h5 {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--teal-800);
    padding-bottom: 10px;
    border-bottom: 2px solid var(--teal-100);
    margin-bottom: 12px;
}

.ps-item p {
    font-size: 0.9rem;
    color: var(--ink-soft);
    margin-bottom: 10px;
}

.ps-item p:last-child {
    margin-bottom: 0;
}

.ps-item p strong {
    display: block;
    color: var(--ink);
    font-weight: 700;
    margin-bottom: 2px;
}

.project-block h4 {
    font-size: 0.8rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--teal-600);
    margin-bottom: 8px;
}

.project-block p {
    font-size: 0.97rem;
    color: var(--ink-soft);
}

.project-details {
    margin-top: 14px;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.project-details li {
    font-size: 0.94rem;
    color: var(--ink-soft);
    padding-left: 16px;
    position: relative;
}

.project-details li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0.55em;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--teal-500);
}

.project-details strong {
    color: var(--ink);
    font-weight: 600;
}

.impact-metric {
    background: var(--teal-50);
    border: 1px solid var(--teal-100);
    border-radius: var(--radius);
    padding: 20px;
    text-align: center;
}

.impact-number {
    display: block;
    font-size: 2.2rem;
    font-weight: 800;
    color: var(--teal-700);
    line-height: 1.1;
    margin-bottom: 4px;
}

.impact-text {
    font-size: 0.9rem;
    color: var(--ink-soft);
    font-weight: 500;
}

.impact-metric-second {
    margin-top: 10px;
}

.architecture-flow {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 8px;
    background: var(--bg-alt);
    border: 1px solid var(--line);
    border-radius: 10px;
    padding: 14px;
    margin-bottom: 14px;
}

.flow-step {
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--teal-800);
    background: var(--white);
    border: 1px solid var(--teal-100);
    padding: 6px 12px;
    border-radius: 8px;
}

.flow-arrow {
    color: var(--teal-500);
    font-weight: 700;
}

.project-tech {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    padding-top: 4px;
}

.project-tech span {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--ink-soft);
    background: var(--bg-alt);
    border: 1px solid var(--line);
    padding: 5px 12px;
    border-radius: 100px;
}

/* ===== RESEARCH GRID ===== */
.research-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
    align-items: stretch;
}

.research-card {
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    padding: 32px;
    box-shadow: var(--shadow-sm);
    display: flex;
    flex-direction: column;
    transition: box-shadow 0.3s ease, transform 0.3s ease;
}

.research-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-3px);
}

.research-card-featured {
    border-top: 3px solid var(--teal-500);
}

.research-badge {
    display: inline-block;
    align-self: flex-start;
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--teal-700);
    background: var(--teal-50);
    border: 1px solid var(--teal-100);
    padding: 4px 12px;
    border-radius: 100px;
    margin-bottom: 18px;
}

.research-card h3 {
    font-size: 1.35rem;
    font-weight: 800;
    letter-spacing: -0.01em;
    margin-bottom: 2px;
}

.research-subtitle {
    font-size: 0.92rem;
    font-weight: 600;
    color: var(--teal-700);
    margin-bottom: 14px;
}

.research-desc {
    font-size: 0.95rem;
    color: var(--ink-soft);
    margin-bottom: 20px;
}

.research-stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    margin-bottom: 20px;
}

.research-stat {
    background: var(--teal-50);
    border: 1px solid var(--teal-100);
    border-radius: 10px;
    padding: 14px 10px;
    text-align: center;
}

.research-stat span {
    display: block;
    font-size: 1.3rem;
    font-weight: 800;
    color: var(--teal-700);
    line-height: 1.1;
}

.research-stat small {
    font-size: 0.72rem;
    color: var(--muted);
    font-weight: 500;
}

.research-list {
    margin-bottom: 20px;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.research-list li {
    font-size: 0.92rem;
    color: var(--ink-soft);
    padding-left: 16px;
    position: relative;
}

.research-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0.55em;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--teal-500);
}

.research-features {
    display: flex;
    flex-direction: column;
    gap: 16px;
    margin-bottom: 20px;
}

.feature-group h4 {
    font-size: 0.82rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--teal-600);
    margin-bottom: 8px;
}

.feature-group ul {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.feature-group li {
    font-size: 0.9rem;
    color: var(--ink-soft);
    padding-left: 16px;
    position: relative;
}

.feature-group li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0.55em;
    width: 5px;
    height: 5px;
    border-radius: 50%;
    background: var(--teal-500);
}

.research-card .btn {
    margin-top: auto;
    align-self: flex-start;
    margin-top: 20px;
}

/* ===== TIMELINE ===== */
.timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
    padding-left: 40px;
}

.timeline-line {
    position: absolute;
    left: 11px;
    top: 0;
    bottom: 0;
    width: 2px;
    background: linear-gradient(180deg, var(--teal-100), var(--teal-500), var(--teal-100));
}

.timeline-item {
    position: relative;
    margin-bottom: 40px;
}

.timeline-dot {
    position: absolute;
    left: -40px;
    top: 8px;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--white);
    border: 3px solid var(--teal-600);
    box-shadow: 0 0 0 4px var(--teal-50);
}

.timeline-content {
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 28px;
    box-shadow: var(--shadow-sm);
    transition: box-shadow 0.3s ease, transform 0.3s ease;
}

.timeline-content:hover {
    box-shadow: var(--shadow-md);
    transform: translateX(4px);
}

.timeline-header {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 4px;
}

.timeline-header h3 {
    font-size: 1.25rem;
    font-weight: 700;
    letter-spacing: -0.01em;
}

.timeline-date {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--teal-700);
    background: var(--teal-50);
    padding: 3px 12px;
    border-radius: 100px;
}

.timeline-company {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--teal-600);
    margin-bottom: 8px;
}

.timeline-desc {
    font-size: 0.95rem;
    color: var(--ink-soft);
    margin-bottom: 14px;
}

.timeline-skills {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.timeline-skills span {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--ink-soft);
    background: var(--bg-alt);
    border: 1px solid var(--line);
    padding: 4px 12px;
    border-radius: 100px;
}

/* ===== HOW I BUILD ===== */
.build-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
}

.build-card {
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 28px;
    box-shadow: var(--shadow-sm);
    transition: box-shadow 0.3s ease, transform 0.3s ease;
}

.build-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-3px);
}

.build-number {
    font-size: 2rem;
    font-weight: 800;
    color: var(--teal-100);
    line-height: 1;
    margin-bottom: 14px;
    transition: color 0.3s ease;
}

.build-card:hover .build-number {
    color: var(--teal-500);
}

.build-card h3 {
    font-size: 1.1rem;
    font-weight: 700;
    margin-bottom: 8px;
}

.build-card p {
    font-size: 0.92rem;
    color: var(--ink-soft);
}

/* ===== STACK ===== */
.stack-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
}

.stack-group {
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 28px;
    box-shadow: var(--shadow-sm);
}

.stack-group h3 {
    font-size: 0.85rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--teal-600);
    margin-bottom: 16px;
}

.stack-items {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.stack-items span {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--ink-soft);
    background: var(--bg-alt);
    border: 1px solid var(--line);
    padding: 6px 14px;
    border-radius: 100px;
    transition: all 0.2s ease;
}

.stack-items span:hover {
    border-color: var(--teal-500);
    color: var(--teal-700);
    background: var(--teal-50);
}

/* ===== ACHIEVEMENT ===== */
.achievement-card {
    display: flex;
    align-items: center;
    gap: 24px;
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    padding: 32px 40px;
    box-shadow: var(--shadow-sm);
    max-width: 800px;
    margin: 0 auto;
}

.achievement-icon {
    font-size: 2rem;
    color: var(--teal-500);
    background: var(--teal-50);
    border: 1px solid var(--teal-100);
    width: 64px;
    height: 64px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.achievement-card h3 {
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 2px;
}

.achievement-card p {
    font-size: 0.9rem;
    color: var(--teal-600);
    font-weight: 600;
    margin-bottom: 6px;
}

.achievement-desc {
    font-size: 0.92rem;
    color: var(--ink-soft);
}

/* ===== ABOUT ===== */
.about-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
    margin-bottom: 48px;
}

.about-card {
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 28px;
    box-shadow: var(--shadow-sm);
    transition: box-shadow 0.3s ease, transform 0.3s ease;
}

.about-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-3px);
}

.about-card h3 {
    font-size: 1.05rem;
    font-weight: 700;
    margin-bottom: 8px;
    color: var(--teal-800);
}

.about-card p {
    font-size: 0.92rem;
    color: var(--ink-soft);
}

.about-personal {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
}

.about-edu,
.about-hobbies {
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 28px;
    box-shadow: var(--shadow-sm);
}

.about-edu h3,
.about-hobbies h3 {
    font-size: 0.85rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--teal-600);
    margin-bottom: 12px;
}

.about-edu p,
.about-hobbies p {
    font-size: 0.95rem;
    color: var(--ink-soft);
}

.about-edu strong {
    color: var(--ink);
}

/* ===== CONTACT ===== */
.section-contact {
    background: linear-gradient(135deg, var(--teal-800), var(--teal-600));
    color: var(--white);
    text-align: center;
    padding: 120px 0;
}

.contact-inner {
    max-width: 680px;
    margin: 0 auto;
}

.contact-title {
    font-size: clamp(2rem, 5vw, 3rem);
    font-weight: 800;
    letter-spacing: -0.02em;
    margin-bottom: 20px;
}

.contact-desc {
    font-size: 1.1rem;
    color: rgba(255, 255, 255, 0.9);
    margin-bottom: 40px;
    line-height: 1.7;
}

.contact-actions {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 12px;
}

/* ===== LIVE DEMO MODAL ===== */
.demo-modal {
    position: fixed;
    inset: 0;
    z-index: 200;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
    visibility: hidden;
    opacity: 0;
    transition: opacity 0.25s ease, visibility 0.25s ease;
}

.demo-modal.open {
    visibility: visible;
    opacity: 1;
}

.demo-overlay {
    position: absolute;
    inset: 0;
    background: rgba(15, 76, 71, 0.45);
    backdrop-filter: blur(3px);
    -webkit-backdrop-filter: blur(3px);
}

.demo-panel {
    position: relative;
    background: var(--white);
    border-radius: var(--radius-lg);
    padding: 36px;
    max-width: 460px;
    width: 100%;
    box-shadow: var(--shadow-lg);
    transform: translateY(12px) scale(0.98);
    transition: transform 0.25s ease;
}

.demo-modal.open .demo-panel {
    transform: translateY(0) scale(1);
}

.demo-close {
    position: absolute;
    top: 16px;
    right: 16px;
    background: none;
    border: none;
    font-size: 1.6rem;
    line-height: 1;
    color: var(--muted);
    cursor: pointer;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    transition: background 0.2s ease, color 0.2s ease;
}

.demo-close:hover {
    background: var(--bg-alt);
    color: var(--teal-700);
}

.demo-panel h3 {
    font-size: 1.4rem;
    font-weight: 800;
    letter-spacing: -0.02em;
    margin-bottom: 6px;
}

.demo-sub {
    font-size: 0.95rem;
    color: var(--muted);
    margin-bottom: 24px;
}

.demo-options {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.demo-option {
    display: flex;
    flex-direction: column;
    gap: 2px;
    padding: 18px 20px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    transition: border-color 0.2s ease, background 0.2s ease, transform 0.2s ease;
}

.demo-option:hover {
    border-color: var(--teal-500);
    background: var(--teal-50);
    transform: translateX(4px);
}

.demo-opt-title {
    font-size: 1.05rem;
    font-weight: 700;
    color: var(--ink);
}

.demo-opt-sub {
    font-size: 0.85rem;
    color: var(--muted);
}

/* ===== FOOTER ===== */
.footer {
    background: var(--teal-900);
    color: rgba(255, 255, 255, 0.7);
    padding: 32px 0;
}

.footer-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 16px;
}

.footer-inner span {
    font-size: 0.85rem;
}

.footer-links {
    display: flex;
    gap: 20px;
}

.footer-links a {
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.7);
    transition: color 0.2s ease;
}

.footer-links a:hover {
    color: var(--white);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 900px) {
    .hero-stats {
        grid-template-columns: repeat(2, 1fr);
    }
    .project-grid {
        grid-template-columns: 1fr;
    }
    .problem-solution-list {
        grid-template-columns: 1fr;
    }
    .research-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    .build-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    .stack-grid {
        grid-template-columns: 1fr;
    }
    .about-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 720px) {
    .nav-toggle {
        display: flex;
    }
    .nav-links {
        position: fixed;
        top: 72px;
        left: 0;
        right: 0;
        flex-direction: column;
        background: var(--white);
        border-bottom: 1px solid var(--line);
        box-shadow: var(--shadow-md);
        padding: 16px 24px 24px;
        gap: 6px;
        align-items: stretch;
        transform: translateY(-16px);
        opacity: 0;
        pointer-events: none;
        transition: transform 0.3s ease, opacity 0.3s ease;
    }
    .nav-links.open {
        transform: translateY(0);
        opacity: 1;
        pointer-events: auto;
    }
    .nav-links a {
        text-align: center;
        padding: 12px;
    }
    .section {
        padding: 72px 0;
    }
    .research-grid {
        grid-template-columns: 1fr;
    }
    .build-grid {
        grid-template-columns: 1fr;
    }
    .about-grid {
        grid-template-columns: 1fr;
    }
    .about-personal {
        grid-template-columns: 1fr;
    }
    .hero {
        padding: 100px 0 60px;
    }
    .project-card {
        padding: 24px;
    }
    .timeline {
        padding-left: 32px;
    }
    .timeline-dot {
        left: -32px;
        width: 20px;
        height: 20px;
    }
    .timeline-line {
        left: 9px;
    }
    .achievement-card {
        flex-direction: column;
        text-align: center;
        padding: 28px 24px;
    }
    .contact-actions {
        flex-direction: column;
        align-items: stretch;
    }
    .contact-actions .btn {
        width: 100%;
    }
}

@media (max-width: 480px) {
    .hero-stats {
        grid-template-columns: 1fr 1fr;
        gap: 12px;
    }
    .stat-card {
        padding: 16px 12px;
    }
    .stat-number {
        font-size: 1.6rem;
    }
    .hero-actions {
        flex-direction: column;
        align-items: stretch;
    }
    .hero-actions .btn {
        width: 100%;
    }
}