/* ============================================================
   Personal Website — Main Stylesheet
   Design: Dark theme with teal/mint accent
   Fonts: Syne (headings) + JetBrains Mono (body)
   Pure CSS — no frameworks
   ============================================================ */

/* --- CSS Custom Properties (Design Tokens) ----------------- */
:root {
    /* Background colors */
    --bg-primary: #0B0F19;
    --bg-secondary: #151B2B;
    --bg-tertiary: #1C2333;
    --bg-hover: #232D42;

    /* Accent / Brand colors */
    --accent: #64FFDA;
    --accent-dark: #3DD6AD;
    --accent-glow: rgba(100, 255, 218, 0.15);
    --accent-subtle: rgba(100, 255, 218, 0.08);

    /* Text colors */
    --text-primary: #E6F1FF;
    --text-secondary: #8892B0;
    --text-tertiary: #495670;
    --text-accent: #64FFDA;

    /* Border & dividers */
    --border: #1E2A3A;
    --border-accent: rgba(100, 255, 218, 0.3);

    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.25);
    --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.35);
    --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.45);
    --shadow-accent: 0 0 30px rgba(100, 255, 218, 0.1);

    /* Typography */
    --font-heading: 'Syne', sans-serif;
    --font-body: 'JetBrains Mono', monospace;

    /* Spacing */
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 5rem;

    /* Border radius */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --radius-xl: 20px;
    --radius-full: 9999px;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 400ms ease;

    /* Layout */
    --max-width: 1200px;
    --header-height: 72px;
}

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

html {
    scroll-behavior: smooth;
    font-size: 16px;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-body);
    font-size: 0.9375rem;
    line-height: 1.7;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    min-height: 100vh;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* --- Typography -------------------------------------------- */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-heading);
    font-weight: 700;
    line-height: 1.2;
    color: var(--text-primary);
}

h1 { font-size: clamp(2.5rem, 6vw, 4rem); letter-spacing: -0.02em; }
h2 { font-size: clamp(1.75rem, 4vw, 2.5rem); letter-spacing: -0.01em; }
h3 { font-size: clamp(1.125rem, 2.5vw, 1.5rem); }
h4 { font-size: 1.125rem; }

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

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

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

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

/* --- Scrollbar --------------------------------------------- */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--bg-primary); }
::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: var(--radius-full);
}
::-webkit-scrollbar-thumb:hover { background: var(--text-tertiary); }

/* --- Selection -------------------------------------------- */
::selection {
    background: var(--accent);
    color: var(--bg-primary);
}

/* --- Layout Utilities ------------------------------------- */
.container {
    width: 100%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-xl);
}

.section {
    padding: var(--space-3xl) 0;
}

.section-header {
    margin-bottom: var(--space-2xl);
}

.section-title {
    position: relative;
    display: inline-block;
    margin-bottom: var(--space-sm);
}

/* Accent line under section titles */
.section-title::after {
    content: '';
    position: absolute;
    bottom: -6px;
    left: 0;
    width: 60px;
    height: 3px;
    background: var(--accent);
    border-radius: var(--radius-full);
}

/* --- Cards ------------------------------------------------- */
.card {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-xl);
    box-shadow: var(--shadow-md);
    transition:
        transform var(--transition-base),
        box-shadow var(--transition-base),
        border-color var(--transition-base);
}

.card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg), var(--shadow-accent);
    border-color: var(--border-accent);
}

/* --- Buttons ---------------------------------------------- */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: 0.75rem 1.75rem;
    font-family: var(--font-body);
    font-size: 0.875rem;
    font-weight: 600;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    border: 2px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition:
        background var(--transition-fast),
        color var(--transition-fast),
        border-color var(--transition-fast),
        transform var(--transition-fast),
        box-shadow var(--transition-fast);
    text-decoration: none;
    white-space: nowrap;
}

.btn:active { transform: scale(0.97); }

.btn-primary {
    background: var(--accent);
    color: var(--bg-primary);
    border-color: var(--accent);
}

.btn-primary:hover {
    background: var(--accent-dark);
    border-color: var(--accent-dark);
    color: var(--bg-primary);
    box-shadow: 0 0 20px rgba(100, 255, 218, 0.3);
}

.btn-ghost {
    background: transparent;
    color: var(--accent);
    border-color: var(--border-accent);
}

.btn-ghost:hover {
    background: var(--accent-subtle);
    border-color: var(--accent);
    color: var(--accent);
    box-shadow: var(--shadow-accent);
}

.btn-sm {
    padding: 0.5rem 1.25rem;
    font-size: 0.8125rem;
}

/* --- Header / Navigation ---------------------------------- */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    height: var(--header-height);
    background: rgba(11, 15, 25, 0.85);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--border);
    transition: background var(--transition-base);
}

.header.scrolled {
    background: rgba(11, 15, 25, 0.95);
    box-shadow: var(--shadow-sm);
}

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

/* Logo */
.logo {
    font-family: var(--font-heading);
    font-size: 1.375rem;
    font-weight: 800;
    color: var(--text-primary);
    text-decoration: none;
    letter-spacing: -0.02em;
}

.logo-accent { color: var(--accent); }

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

/* Desktop Navigation */
.nav-desktop {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.nav-link {
    position: relative;
    padding: 0.5rem 1rem;
    font-size: 0.8125rem;
    font-weight: 500;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-secondary);
    text-decoration: none;
    transition: color var(--transition-fast);
    border-radius: var(--radius-sm);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 4px;
    left: 1rem;
    right: 1rem;
    height: 2px;
    background: var(--accent);
    border-radius: var(--radius-full);
    transform: scaleX(0);
    transform-origin: right;
    transition: transform var(--transition-base);
}

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

.nav-link:hover::after,
.nav-link.active::after {
    transform: scaleX(1);
    transform-origin: left;
}

/* Hamburger button (mobile) */
.hamburger {
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 44px;
    height: 44px;
    padding: 8px;
    background: transparent;
    border: none;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: background var(--transition-fast);
    z-index: 1001;
}

.hamburger:hover { background: var(--bg-tertiary); }

.hamburger-line {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--text-primary);
    border-radius: var(--radius-full);
    transition:
        transform var(--transition-base),
        opacity var(--transition-base);
}

.hamburger-line:nth-child(1) { margin-bottom: 6px; }
.hamburger-line:nth-child(2) { margin-bottom: 6px; }

/* Hamburger → X animation when menu is open */
.hamburger.open .hamburger-line:nth-child(1) {
    transform: translateY(8px) rotate(45deg);
}
.hamburger.open .hamburger-line:nth-child(2) {
    opacity: 0;
    transform: scaleX(0);
}
.hamburger.open .hamburger-line:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
}

/* Mobile Navigation Overlay */
.nav-mobile {
    display: none;
    position: fixed;
    inset: 0;
    z-index: 999;
    background: rgba(11, 15, 25, 0.98);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: var(--space-lg);
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--transition-base);
}

.nav-mobile.open {
    opacity: 1;
    pointer-events: all;
}

.nav-mobile-link {
    font-family: var(--font-heading);
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-secondary);
    text-decoration: none;
    transition: color var(--transition-fast), transform var(--transition-fast);
    letter-spacing: -0.01em;
}

.nav-mobile-link:hover,
.nav-mobile-link.active {
    color: var(--accent);
    transform: scale(1.05);
}

/* --- Hero Section ----------------------------------------- */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding-top: var(--header-height);
    overflow: hidden;
}

/* Subtle grid background pattern */
.hero::before {
    content: '';
    position: absolute;
    inset: 0;
    background-image:
        linear-gradient(var(--border) 1px, transparent 1px),
        linear-gradient(90deg, var(--border) 1px, transparent 1px);
    background-size: 60px 60px;
    opacity: 0.3;
    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%);
}

/* Ambient glow */
.hero::after {
    content: '';
    position: absolute;
    top: 20%;
    left: 50%;
    transform: translateX(-50%);
    width: 600px;
    height: 400px;
    background: radial-gradient(ellipse, rgba(100, 255, 218, 0.06) 0%, transparent 70%);
    pointer-events: none;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
}

.hero-eyebrow {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    margin-bottom: var(--space-lg);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--accent);
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.hero-eyebrow::before {
    content: '';
    display: block;
    width: 40px;
    height: 1px;
    background: var(--accent);
}

.hero-title {
    margin-bottom: var(--space-lg);
}

.hero-title .name {
    display: block;
    color: var(--text-primary);
}

.hero-title .title {
    display: block;
    font-size: clamp(1.5rem, 4vw, 2.5rem);
    color: var(--text-secondary);
    font-weight: 400;
    margin-top: 0.25rem;
}

.hero-title .cursor {
    display: inline-block;
    width: 4px;
    height: 1em;
    background: var(--accent);
    margin-left: 4px;
    vertical-align: middle;
    border-radius: var(--radius-full);
    animation: blink 1.2s step-end infinite;
}

@keyframes blink {
    0%, 100% { opacity: 1; }
    50% { opacity: 0; }
}

.hero-description {
    font-size: 1.125rem;
    max-width: 540px;
    margin-bottom: var(--space-2xl);
    line-height: 1.8;
}

.hero-cta {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-md);
}

/* --- Intro / About preview section ------------------------ */
.intro-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-2xl);
    align-items: center;
}

.intro-text p {
    margin-bottom: var(--space-md);
    font-size: 1rem;
    line-height: 1.9;
}

.intro-text p:last-child { margin-bottom: 0; }

.intro-stats {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-md);
    margin-top: var(--space-xl);
}

.stat-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    text-align: center;
    transition: transform var(--transition-base), border-color var(--transition-base);
}

.stat-card:hover {
    transform: translateY(-4px);
    border-color: var(--border-accent);
}

.stat-number {
    font-family: var(--font-heading);
    font-size: 2rem;
    font-weight: 800;
    color: var(--accent);
    line-height: 1;
    margin-bottom: var(--space-sm);
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

/* --- Featured Cards --------------------------------------- */
.featured-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--space-lg);
}

.featured-card {
    padding: var(--space-xl);
}

.featured-icon {
    width: 52px;
    height: 52px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--accent-subtle);
    border: 1px solid var(--border-accent);
    border-radius: var(--radius-md);
    font-size: 1.5rem;
    margin-bottom: var(--space-lg);
    transition: background var(--transition-base), transform var(--transition-base);
}

.card:hover .featured-icon {
    background: var(--accent-glow);
    transform: scale(1.05);
}

.featured-card h3 {
    margin-bottom: var(--space-sm);
    color: var(--text-primary);
}

.featured-card p {
    font-size: 0.875rem;
    line-height: 1.7;
    margin-bottom: var(--space-lg);
}

.featured-link {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--accent);
    letter-spacing: 0.05em;
    text-transform: uppercase;
    transition: gap var(--transition-fast);
}

.featured-link:hover {
    gap: var(--space-sm);
    color: var(--accent-dark);
}

/* Arrow icon for links */
.featured-link::after {
    content: '→';
    transition: transform var(--transition-fast);
}
.featured-link:hover::after { transform: translateX(4px); }

/* --- About Page ------------------------------------------- */
.about-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-2xl);
    align-items: start;
}

@media (min-width: 768px) {
    .about-grid {
        grid-template-columns: 1fr 1.5fr;
    }
}

.about-image-wrapper {
    position: relative;
}

.about-image {
    width: 100%;
    max-width: 320px;
    aspect-ratio: 1;
    object-fit: cover;
    border-radius: var(--radius-lg);
    border: 2px solid var(--border);
    background: var(--bg-tertiary);
    display: block;
    margin: 0 auto;
    transition: border-color var(--transition-base);
}

.about-image:hover { border-color: var(--border-accent); }

/* Decorative accent frame */
.about-image-wrapper::before {
    content: '';
    position: absolute;
    top: 12px;
    left: 12px;
    right: -12px;
    bottom: -12px;
    border: 2px solid var(--accent);
    border-radius: var(--radius-lg);
    opacity: 0.3;
    z-index: -1;
}

.about-bio p {
    margin-bottom: var(--space-md);
    line-height: 1.9;
}

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

/* Skills Section */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: var(--space-xl);
}

.skill-category h3 {
    font-family: var(--font-heading);
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: var(--space-lg);
    letter-spacing: 0.02em;
}

.skill-item {
    margin-bottom: var(--space-md);
}

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

.skill-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-sm);
}

.skill-name {
    font-size: 0.8125rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.skill-percent {
    font-size: 0.75rem;
    color: var(--accent);
    font-weight: 600;
}

.skill-bar-track {
    height: 6px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-full);
    overflow: hidden;
}

.skill-bar-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--accent-dark), var(--accent));
    border-radius: var(--radius-full);
    width: 0;
    transition: width 1.2s cubic-bezier(0.22, 1, 0.36, 1);
}

/* --- Links Page ------------------------------------------- */
.links-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--space-lg);
}

.link-card {
    padding: var(--space-xl);
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
    cursor: pointer;
}

.link-card-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 1.375rem;
    transition: background var(--transition-base), border-color var(--transition-base), transform var(--transition-base);
}

.card:hover .link-card-icon {
    background: var(--accent-subtle);
    border-color: var(--border-accent);
    transform: scale(1.05);
}

.link-card h3 {
    font-size: 1.0625rem;
    margin: 0;
}

.link-card p {
    font-size: 0.875rem;
    line-height: 1.7;
    flex-grow: 1;
}

.link-card-footer {
    margin-top: auto;
    padding-top: var(--space-md);
    border-top: 1px solid var(--border);
}

.link-card-url {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    word-break: break-all;
}

/* --- Contact Page ----------------------------------------- */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-2xl);
}

@media (min-width: 768px) {
    .contact-grid {
        grid-template-columns: 1fr 1fr;
    }
}

.contact-info h2 {
    margin-bottom: var(--space-md);
}

.contact-info > p {
    margin-bottom: var(--space-xl);
    line-height: 1.8;
}

.contact-detail {
    display: flex;
    align-items: flex-start;
    gap: var(--space-md);
    margin-bottom: var(--space-lg);
    padding: var(--space-md);
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    transition: border-color var(--transition-fast);
}

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

.contact-detail-icon {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--accent-subtle);
    border: 1px solid var(--border-accent);
    border-radius: var(--radius-sm);
    font-size: 1.125rem;
    flex-shrink: 0;
}

.contact-detail-label {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    letter-spacing: 0.08em;
    text-transform: uppercase;
    margin-bottom: 2px;
}

.contact-detail-value {
    font-size: 0.9375rem;
    color: var(--text-primary);
}

/* --- Forms ------------------------------------------------ */
.form-group {
    margin-bottom: var(--space-lg);
}

.form-label {
    display: block;
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--text-secondary);
    letter-spacing: 0.06em;
    text-transform: uppercase;
    margin-bottom: var(--space-sm);
}

.form-input,
.form-textarea {
    width: 100%;
    padding: 0.875rem 1rem;
    font-family: var(--font-body);
    font-size: 0.9375rem;
    color: var(--text-primary);
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    outline: none;
    transition:
        border-color var(--transition-fast),
        box-shadow var(--transition-fast),
        background var(--transition-fast);
    -webkit-appearance: none;
}

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

.form-input:focus,
.form-textarea:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
    background: var(--bg-hover);
}

.form-textarea {
    min-height: 160px;
    resize: vertical;
    line-height: 1.7;
}

/* Form validation states */
.form-group.error .form-input,
.form-group.error .form-textarea {
    border-color: #FF6B6B;
    box-shadow: 0 0 0 3px rgba(255, 107, 107, 0.1);
}

.form-group.success .form-input,
.form-group.success .form-textarea {
    border-color: #51CF66;
}

.form-error {
    display: none;
    margin-top: var(--space-sm);
    font-size: 0.8125rem;
    color: #FF6B6B;
}

.form-group.error .form-error { display: block; }

/* --- Alert / Status Messages ------------------------------ */
.alert {
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    margin-bottom: var(--space-xl);
    border: 1px solid;
    display: none;
    align-items: flex-start;
    gap: var(--space-sm);
}

.alert.show { display: flex; }

.alert-success {
    background: rgba(81, 207, 102, 0.08);
    border-color: rgba(81, 207, 102, 0.3);
    color: #51CF66;
}

.alert-error {
    background: rgba(255, 107, 107, 0.08);
    border-color: rgba(255, 107, 107, 0.3);
    color: #FF6B6B;
}

.alert-icon { font-size: 1.125rem; flex-shrink: 0; }

/* --- Footer ----------------------------------------------- */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border);
    padding: var(--space-2xl) 0;
}

.footer-inner {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-xl);
    text-align: center;
}

.footer-logo {
    font-family: var(--font-heading);
    font-size: 1.25rem;
    font-weight: 800;
    color: var(--text-primary);
    text-decoration: none;
    letter-spacing: -0.02em;
}

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

.footer-social {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.footer-social-link {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 1.125rem;
    color: var(--text-secondary);
    text-decoration: none;
    transition:
        background var(--transition-fast),
        border-color var(--transition-fast),
        color var(--transition-fast),
        transform var(--transition-fast);
}

.footer-social-link:hover {
    background: var(--accent-subtle);
    border-color: var(--border-accent);
    color: var(--accent);
    transform: translateY(-3px);
}

.footer-bottom {
    font-size: 0.8125rem;
    color: var(--text-tertiary);
}

/* --- Scroll-to-Top Button -------------------------------- */
.scroll-top {
    position: fixed;
    bottom: var(--space-xl);
    right: var(--space-xl);
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-secondary);
    border: 1px solid var(--border-accent);
    border-radius: var(--radius-md);
    color: var(--accent);
    font-size: 1.25rem;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(16px);
    transition:
        opacity var(--transition-base),
        visibility var(--transition-base),
        transform var(--transition-base),
        background var(--transition-fast),
        border-color var(--transition-fast),
        box-shadow var(--transition-fast);
    z-index: 900;
    box-shadow: var(--shadow-md);
}

.scroll-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.scroll-top:hover {
    background: var(--accent-subtle);
    border-color: var(--accent);
    box-shadow: var(--shadow-accent);
    transform: translateY(-3px);
}

.scroll-top:active {
    transform: scale(0.95) translateY(0);
}

/* --- Responsive ------------------------------------------- */
@media (max-width: 768px) {
    :root {
        --space-xl: 1.5rem;
        --space-2xl: 2rem;
        --space-3xl: 3rem;
    }

    /* Show hamburger, hide desktop nav */
    .nav-desktop { display: none; }
    .hamburger { display: flex; }
    .nav-mobile { display: flex; }

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

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

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

@media (max-width: 480px) {
    .hero-cta {
        flex-direction: column;
    }

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

    .intro-stats {
        grid-template-columns: 1fr 1fr;
    }
}

/* --- Focus visible (accessibility) ------------------------ */
:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 3px;
    border-radius: var(--radius-sm);
}

/* --- Page transitions (subtle fade-in) -------------------- */
.page-content {
    opacity: 0;
    animation: fadeInUp 0.6s ease forwards;
    animation-delay: 0.1s;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* --- Misc / Helpers --------------------------------------- */
.text-accent { color: var(--accent); }
.text-muted { color: var(--text-secondary); }
.text-center { text-align: center; }
.mt-xl { margin-top: var(--space-xl); }
.mb-xl { margin-bottom: var(--space-xl); }