/* ==========================================================================
   Design Tokens & Variables
   ========================================================================== */
:root {
    --bg-main: #090d16;
    --bg-surface: #0f172a;
    --bg-surface-hover: #141e33;
    --bg-elevated: #18233c;
    --bg-subtle: rgba(255, 255, 255, 0.03);
    
    --border-main: rgba(255, 255, 255, 0.07);
    --border-hover: rgba(255, 255, 255, 0.16);
    --border-focus: rgba(96, 165, 250, 0.4);
    
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    --accent: #2563eb;
    --accent-hover: #1d4ed8;
    --accent-light: #60a5fa;
    --accent-glow: rgba(37, 99, 235, 0.15);
    --accent-subtle: rgba(37, 99, 235, 0.08);
    
    --status-active: #10b981;
    --status-glow: rgba(16, 185, 129, 0.25);
    
    --font-sans: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --radius-full: 9999px;
    
    --transition: all 0.22s cubic-bezier(0.16, 1, 0.3, 1);
    --shadow-card: 0 4px 20px rgba(0, 0, 0, 0.25);
    --shadow-card-hover: 0 8px 30px rgba(0, 0, 0, 0.4);
}

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

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

body {
    background-color: var(--bg-main);
    color: var(--text-primary);
    font-family: var(--font-sans);
    line-height: 1.65;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
    position: relative;
}

/* Subtle background ambience */
.bg-glow {
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 1000px;
    height: 550px;
    background: radial-gradient(circle, rgba(37, 99, 235, 0.09) 0%, rgba(9, 13, 22, 0) 70%);
    pointer-events: none;
    z-index: 0;
}

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

button {
    font-family: inherit;
}

.container {
    width: 100%;
    max-width: 980px;
    margin: 0 auto;
    padding: 0 24px;
    position: relative;
    z-index: 1;
}

.section {
    padding: 76px 0;
    border-top: 1px solid var(--border-main);
}

.section-header {
    margin-bottom: 32px;
}

.section-label {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--accent-light);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    display: block;
    margin-bottom: 6px;
}

.section-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.025em;
}

.section-desc {
    color: var(--text-secondary);
    font-size: 0.92rem;
    margin-top: 6px;
    max-width: 640px;
}

/* ==========================================================================
   Header & Navigation
   ========================================================================== */
.header {
    position: sticky;
    top: 0;
    width: 100%;
    z-index: 50;
    background: rgba(9, 13, 22, 0.82);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid var(--border-main);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 60px;
}

.brand {
    display: flex;
    align-items: center;
}

.brand-name {
    font-size: 0.98rem;
    font-weight: 600;
    letter-spacing: -0.01em;
    color: var(--text-primary);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 22px;
}

.nav-link {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-secondary);
    padding: 4px 0;
    position: relative;
}

.nav-link:hover, 
.nav-link.active {
    color: var(--text-primary);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    height: 1.5px;
    background: var(--accent-light);
    border-radius: 2px;
}

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

.btn-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 34px;
    height: 34px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-main);
    color: var(--text-secondary);
    background: var(--bg-surface);
}

.btn-icon:hover {
    color: var(--text-primary);
    border-color: var(--border-hover);
    background: var(--bg-surface-hover);
}

.menu-toggle {
    display: none;
    flex-direction: column;
    justify-content: space-around;
    width: 32px;
    height: 32px;
    background: transparent;
    border: 1px solid var(--border-main);
    border-radius: var(--radius-sm);
    cursor: pointer;
    padding: 6px;
}

.menu-toggle span {
    width: 100%;
    height: 1.5px;
    background-color: var(--text-primary);
    border-radius: 1px;
}

.mobile-menu {
    display: none;
    flex-direction: column;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border-main);
    padding: 16px 24px;
    gap: 12px;
}

.mobile-menu.open {
    display: flex;
}

.mobile-nav-link {
    font-size: 0.95rem;
    color: var(--text-secondary);
    padding: 6px 0;
}

.mobile-nav-link:hover {
    color: var(--text-primary);
}

/* ==========================================================================
   Hero Section
   ========================================================================== */
.hero-section {
    padding: 76px 0 68px 0;
    border-top: none;
}

.hero-container {
    display: flex;
    align-items: center;
    justify-content: flex-start;
    gap: 52px;
}

.hero-content {
    flex: 1;
    max-width: 640px;
}

.status-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background: rgba(16, 185, 129, 0.08);
    border: 1px solid rgba(16, 185, 129, 0.22);
    padding: 5px 14px;
    border-radius: var(--radius-full);
    margin-bottom: 18px;
}

.status-dot {
    width: 7px;
    height: 7px;
    border-radius: 50%;
    background-color: var(--status-active);
    box-shadow: 0 0 8px var(--status-glow);
    animation: pulse-dot 2s infinite ease-in-out;
}

@keyframes pulse-dot {
    0%, 100% {
        transform: scale(1);
        opacity: 1;
    }
    50% {
        transform: scale(1.25);
        opacity: 0.7;
    }
}

.status-text {
    font-size: 0.78rem;
    font-weight: 500;
    color: #a7f3d0;
    letter-spacing: 0.01em;
}

.hero-title {
    font-size: 3rem;
    font-weight: 800;
    letter-spacing: -0.035em;
    color: var(--text-primary);
    line-height: 1.12;
    margin-bottom: 8px;
    background: linear-gradient(180deg, #ffffff 40%, #cbd5e1 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero-subtitle {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--accent-light);
    margin-bottom: 16px;
    letter-spacing: -0.01em;
}

.subtitle-bullet {
    color: var(--text-muted);
    font-size: 0.85em;
    margin: 0 4px;
}

.hero-description {
    font-size: 0.96rem;
    color: var(--text-secondary);
    line-height: 1.68;
    margin-bottom: 22px;
}

.hero-highlights {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 28px;
}

.highlight-pill {
    font-family: var(--font-mono);
    font-size: 0.74rem;
    padding: 3px 10px;
    border-radius: var(--radius-full);
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-main);
    color: var(--text-secondary);
    transition: var(--transition);
}

.highlight-pill:hover {
    color: var(--text-primary);
    border-color: var(--border-hover);
    background: rgba(255, 255, 255, 0.06);
}

.hero-visual {
    position: relative;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
}

.hero-avatar-glow {
    position: absolute;
    width: 270px;
    height: 270px;
    background: radial-gradient(circle, rgba(37, 99, 235, 0.24) 0%, rgba(37, 99, 235, 0) 70%);
    border-radius: 50%;
    pointer-events: none;
    z-index: 0;
    filter: blur(14px);
}

.hero-avatar-frame {
    position: relative;
    z-index: 1;
    width: 215px;
    height: 215px;
    border-radius: var(--radius-full);
    padding: 3px;
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.18) 0%, rgba(255, 255, 255, 0.03) 100%);
    box-shadow: 0 18px 40px rgba(0, 0, 0, 0.5);
}

.hero-avatar {
    width: 100%;
    height: 100%;
    border-radius: var(--radius-full);
    object-fit: cover;
    display: block;
}

.hero-cta-group {
    display: flex;
    align-items: center;
    gap: 12px;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 9px 18px;
    border-radius: var(--radius-md);
    font-size: 0.86rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.btn-primary {
    background: var(--accent);
    color: #ffffff;
    border: 1px solid transparent;
    box-shadow: 0 2px 10px rgba(37, 99, 235, 0.25);
}

.btn-primary:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
    box-shadow: 0 4px 14px rgba(37, 99, 235, 0.35);
}

.btn-secondary {
    background: var(--bg-surface);
    color: var(--text-primary);
    border: 1px solid var(--border-main);
}

.btn-secondary:hover {
    background: var(--bg-surface-hover);
    border-color: var(--border-hover);
    transform: translateY(-1px);
}

/* ==========================================================================
   About Section
   ========================================================================== */
.about-grid {
    display: grid;
    grid-template-columns: 1.4fr 1fr;
    gap: 20px;
}

.about-card {
    background: var(--bg-surface);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-card);
}

.main-about p {
    color: var(--text-secondary);
    font-size: 0.92rem;
    margin-bottom: 14px;
    line-height: 1.65;
}

.main-about p:last-child {
    margin-bottom: 0;
}

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

.info-card {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    gap: 12px;
}

.info-row {
    display: flex;
    flex-direction: column;
    gap: 2px;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-main);
}

.info-row:last-child {
    padding-bottom: 0;
    border-bottom: none;
}

.info-label {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--text-muted);
}

.info-value {
    font-size: 0.88rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* ==========================================================================
   Experience Section
   ========================================================================== */
.experience-list {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.exp-card {
    background: var(--bg-surface);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-card);
    transition: var(--transition);
}

.exp-card:hover {
    border-color: var(--border-hover);
    background: var(--bg-surface-hover);
}

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

.exp-header-left {
    display: flex;
    align-items: center;
    gap: 14px;
}

.org-logo {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    width: 42px;
    height: 42px;
    border-radius: var(--radius-md);
    background: var(--bg-elevated);
    border: 1px solid var(--border-main);
    overflow: hidden;
    padding: 2px;
}

.org-logo img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    border-radius: calc(var(--radius-md) - 3px);
}

.org-logo-ebtrans-bg,
.org-logo-hanyang-bg,
.org-logo-sg-bg {
    background: #ffffff;
    padding: 3px;
}

.org-logo-ebtrans-bg img,
.org-logo-hanyang-bg img,
.org-logo-sg-bg img {
    object-fit: contain;
}

.exp-role {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text-primary);
    letter-spacing: -0.01em;
}

.exp-company {
    font-size: 0.86rem;
    font-weight: 500;
    color: var(--accent-light);
    margin-top: 2px;
}

.exp-date {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--text-muted);
    white-space: nowrap;
}

.exp-intro {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 12px;
    line-height: 1.6;
}

.exp-bullets {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.exp-bullets li {
    font-size: 0.88rem;
    color: var(--text-secondary);
    position: relative;
    padding-left: 14px;
    line-height: 1.55;
}

.exp-bullets li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 9px;
    width: 4px;
    height: 4px;
    border-radius: 50%;
    background: var(--accent-light);
}

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

/* ==========================================================================
   Projects Section
   ========================================================================== */
.filter-container {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 6px;
    margin-bottom: 24px;
}

.filter-btn {
    padding: 5px 12px;
    border-radius: var(--radius-sm);
    background: var(--bg-surface);
    border: 1px solid var(--border-main);
    color: var(--text-secondary);
    font-size: 0.8rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.filter-btn:hover {
    color: var(--text-primary);
    border-color: var(--border-hover);
}

.filter-btn.active {
    background: var(--accent);
    color: #ffffff;
    border-color: var(--accent);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
}

.project-card {
    background: var(--bg-surface);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-lg);
    padding: 22px;
    display: flex;
    flex-direction: column;
    box-shadow: var(--shadow-card);
    transition: var(--transition);
}

.project-card:hover {
    border-color: var(--border-hover);
    background: var(--bg-surface-hover);
    transform: translateY(-2px);
    box-shadow: var(--shadow-card-hover);
}

.project-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 10px;
}

.project-tag {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    font-weight: 500;
    color: var(--accent-light);
    background: var(--accent-subtle);
    border: 1px solid rgba(96, 165, 250, 0.15);
    padding: 2px 8px;
    border-radius: var(--radius-sm);
}

.project-actions {
    display: flex;
    align-items: center;
    gap: 6px;
}

.project-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-main);
    color: var(--text-secondary);
    background: var(--bg-elevated);
}

.project-link:hover {
    color: var(--text-primary);
    border-color: var(--border-hover);
    background: var(--accent);
}

.project-title {
    font-size: 1.08rem;
    font-weight: 600;
    letter-spacing: -0.01em;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.project-summary {
    font-size: 0.88rem;
    color: var(--text-secondary);
    line-height: 1.55;
    margin-bottom: 16px;
    flex-grow: 1;
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.tag {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    padding: 2px 7px;
    border-radius: var(--radius-sm);
    background: var(--bg-subtle);
    border: 1px solid var(--border-main);
    color: var(--text-muted);
}

/* ==========================================================================
   Skills Section
   ========================================================================== */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
    margin-bottom: 20px;
}

.skill-card {
    background: var(--bg-surface);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-lg);
    padding: 22px;
    box-shadow: var(--shadow-card);
}

.skill-card h3 {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--text-primary);
    border-bottom: 1px solid var(--border-main);
    padding-bottom: 8px;
}

.skill-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 7px;
}

.skill-list li {
    font-size: 0.84rem;
    color: var(--text-secondary);
    position: relative;
    padding-left: 12px;
}

.skill-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 8px;
    width: 3px;
    height: 3px;
    border-radius: 50%;
    background: var(--accent-light);
}

/* Certifications */
.certifications-box {
    background: var(--bg-surface);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-lg);
    padding: 22px;
    box-shadow: var(--shadow-card);
}

.cert-title {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 14px;
    color: var(--text-primary);
}

.cert-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
}

.cert-item {
    background: var(--bg-main);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-md);
    padding: 12px 14px;
    display: flex;
    flex-direction: column;
    gap: 3px;
}

.cert-name {
    font-size: 0.88rem;
    font-weight: 600;
    color: var(--text-primary);
}

.cert-detail {
    font-size: 0.76rem;
    color: var(--text-muted);
}

/* ==========================================================================
   Timeline / Formation
   ========================================================================== */
.timeline {
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.timeline-item {
    background: var(--bg-surface);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-lg);
    padding: 22px;
    box-shadow: var(--shadow-card);
}

.timeline-header {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    margin-bottom: 8px;
    gap: 14px;
}

.timeline-title {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text-primary);
    letter-spacing: -0.01em;
}

.timeline-sub {
    font-size: 0.86rem;
    font-weight: 500;
    color: var(--accent-light);
    margin-top: 2px;
}

.timeline-date {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--text-muted);
    white-space: nowrap;
}

.timeline-desc {
    font-size: 0.88rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ==========================================================================
   Contact Section
   ========================================================================== */
.contact-box {
    background: var(--bg-surface);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-lg);
    padding: 32px;
    box-shadow: var(--shadow-card);
}

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

.contact-card {
    background: var(--bg-main);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-md);
    padding: 14px 16px;
    display: flex;
    flex-direction: column;
    gap: 3px;
    transition: var(--transition);
}

.contact-card:hover {
    border-color: var(--border-hover);
}

.contact-label {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--text-muted);
}

.contact-action-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 8px;
}

.contact-link {
    font-size: 0.84rem;
    font-weight: 500;
    color: var(--text-primary);
    word-break: break-all;
}

.link-arrow {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    color: var(--accent-light);
}

.link-arrow:hover {
    color: var(--text-primary);
}

.btn-copy {
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    transition: var(--transition);
}

.btn-copy:hover {
    color: var(--text-primary);
}

.copy-tooltip {
    position: absolute;
    bottom: 125%;
    left: 50%;
    transform: translateX(-50%);
    background: var(--status-active);
    color: #ffffff;
    font-size: 0.68rem;
    font-family: var(--font-mono);
    padding: 2px 6px;
    border-radius: 4px;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s ease;
}

.btn-copy.copied .copy-tooltip {
    opacity: 1;
}

/* ==========================================================================
   Toast Notification
   ========================================================================== */
.toast {
    position: fixed;
    bottom: 24px;
    right: 24px;
    background: var(--bg-surface);
    border: 1px solid var(--border-hover);
    color: var(--text-primary);
    padding: 10px 16px;
    border-radius: var(--radius-md);
    font-size: 0.82rem;
    font-weight: 500;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.45);
    transform: translateY(100px);
    opacity: 0;
    pointer-events: none;
    transition: transform 0.25s ease, opacity 0.25s ease;
    z-index: 100;
}

.toast.show {
    transform: translateY(0);
    opacity: 1;
}

/* ==========================================================================
   Footer
   ========================================================================== */
.footer {
    position: relative;
    padding: 34px 0;
    background: linear-gradient(180deg, rgba(9, 13, 22, 0.4) 0%, rgba(15, 23, 42, 0.6) 100%);
    overflow: hidden;
    border-top: 1px solid var(--border-main);
}

/* Animated subtle top border beam */
.footer::before {
    content: '';
    position: absolute;
    top: -1px;
    left: -100%;
    width: 300%;
    height: 1.5px;
    background: linear-gradient(90deg, 
        transparent 0%, 
        rgba(37, 99, 235, 0.1) 20%, 
        var(--accent-light) 50%, 
        rgba(37, 99, 235, 0.1) 80%, 
        transparent 100%
    );
    animation: footerBeam 9s linear infinite;
}

@keyframes footerBeam {
    0% {
        transform: translateX(0%);
    }
    100% {
        transform: translateX(33.333%);
    }
}

.footer-glow {
    position: absolute;
    bottom: -90px;
    left: 50%;
    transform: translateX(-50%);
    width: 620px;
    height: 180px;
    background: radial-gradient(ellipse, rgba(37, 99, 235, 0.14) 0%, rgba(9, 13, 22, 0) 70%);
    pointer-events: none;
    z-index: 0;
    animation: footerPulse 6s ease-in-out infinite alternate;
}

@keyframes footerPulse {
    0% {
        opacity: 0.4;
        transform: translateX(-50%) scale(0.95);
    }
    100% {
        opacity: 0.9;
        transform: translateX(-50%) scale(1.05);
    }
}

.footer-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 0.84rem;
    color: var(--text-muted);
    position: relative;
    z-index: 1;
}

.footer-left {
    display: flex;
    align-items: center;
    gap: 10px;
}

.footer-dot {
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background-color: var(--accent-light);
    box-shadow: 0 0 8px rgba(96, 165, 250, 0.7);
    animation: footerDotPulse 2.5s infinite ease-in-out;
}

@keyframes footerDotPulse {
    0%, 100% {
        transform: scale(1);
        opacity: 0.6;
    }
    50% {
        transform: scale(1.3);
        opacity: 1;
    }
}

.back-to-top {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-main);
    color: var(--text-secondary);
    background: var(--bg-surface);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.back-to-top svg {
    transition: transform 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

.back-to-top:hover {
    color: var(--text-primary);
    border-color: var(--border-hover);
    background: var(--bg-surface-hover);
    box-shadow: 0 0 14px rgba(37, 99, 235, 0.25);
    transform: translateY(-2px);
}

.back-to-top:hover svg {
    transform: translateY(-2px);
}

/* ==========================================================================
   Responsive
   ========================================================================== */
@media (max-width: 850px) {
    .hero-section {
        padding: 56px 0 48px 0;
    }

    .hero-container {
        flex-direction: column;
        align-items: center;
        text-align: center;
        gap: 32px;
    }

    .hero-content {
        max-width: 100%;
    }

    .hero-highlights {
        justify-content: center;
    }

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

    .hero-title {
        font-size: 2.5rem;
    }

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

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

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

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

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

@media (max-width: 650px) {
    .nav-links {
        display: none;
    }
    
    .menu-toggle {
        display: flex;
    }

    .hero-avatar-frame {
        width: 130px;
        height: 130px;
    }

    .hero-avatar-glow {
        width: 160px;
        height: 160px;
    }

    .hero-title {
        font-size: 2.15rem;
    }

    .hero-cta-group {
        flex-direction: column;
        width: 100%;
    }

    .hero-cta-group .btn {
        width: 100%;
        justify-content: center;
    }

    .exp-header, 
    .timeline-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 6px;
    }
}