/* ==========================================================================
   Portfolio — 2026 design system
   1. Tokens          2. Base & reset      3. Utilities
   4. Navigation      5. Hero & metrics    6. About
   7. Timeline        8. Projects          9. Publication
   10. Skills         11. Blog             12. Contact
   13. Footer         14. Motion           15. Responsive
   ========================================================================== */

/* ---------- 1. Tokens ---------- */
:root {
    /* Color */
    --bg: #0a0f24;
    --bg-soft: #101731;
    --surface: rgba(255, 255, 255, 0.04);
    --surface-raised: rgba(255, 255, 255, 0.07);
    --surface-deep: rgba(0, 0, 0, 0.22);
    --line: rgba(255, 255, 255, 0.10);
    --line-strong: rgba(255, 255, 255, 0.18);
    --text: #f2f5ff;
    --muted: #bcc7e3;
    --faint: #9aa8cc;
    --accent: #4fc3f7;
    --accent-2: #3b82f6;
    --accent-soft: rgba(79, 195, 247, 0.12);
    --accent-line: rgba(79, 195, 247, 0.32);
    --gradient: linear-gradient(135deg, #4fc3f7 0%, #3b82f6 100%);
    --on-accent: #051225;
    --brown: #a0522d;
    --success: #34d399;

    /* Spacing (8px scale) */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.5rem;
    --space-6: 2rem;
    --space-7: 2.5rem;
    --space-8: 3rem;
    --space-10: 4rem;
    --space-12: 5rem;
    --space-16: 7rem;

    /* Shape & depth */
    --radius-sm: 10px;
    --radius: 16px;
    --radius-lg: 22px;
    --shadow-sm: 0 2px 10px rgba(2, 6, 20, 0.35);
    --shadow-md: 0 12px 32px rgba(2, 6, 20, 0.45);
    --shadow-lg: 0 24px 56px rgba(2, 6, 20, 0.55);
    --glow: 0 8px 28px rgba(59, 130, 246, 0.35);

    /* Type */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', Consolas, monospace;
    --text-xs: 0.8rem;
    --text-sm: 0.9rem;
    --text-base: 1rem;
    --text-md: 1.08rem;
    --text-lg: clamp(1.15rem, 1.6vw, 1.3rem);
    --text-xl: clamp(1.35rem, 2.2vw, 1.6rem);
    --text-2xl: clamp(1.75rem, 3.5vw, 2.5rem);
    --text-hero: clamp(2.4rem, 5.5vw, 3.8rem);

    --max: 1160px;
    --nav-height: 68px;
}

/* ---------- 2. Base & reset ---------- */
*,
*::before,
*::after { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    font-family: var(--font-sans);
    background: var(--bg);
    background-image:
        radial-gradient(ellipse 80% 50% at 20% -10%, rgba(59, 130, 246, 0.15), transparent),
        radial-gradient(ellipse 60% 40% at 90% 10%, rgba(79, 195, 247, 0.08), transparent);
    background-repeat: no-repeat;
    color: var(--text);
    line-height: 1.65;
    -webkit-font-smoothing: antialiased;
    overflow-x: hidden;
}

section { scroll-margin-top: calc(var(--nav-height) + 1rem); }

img { max-width: 100%; }

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

h1, h2, h3, h4, h5, h6 {
    line-height: 1.2;
    letter-spacing: -0.02em;
    text-wrap: balance;
}

:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 3px;
    border-radius: 4px;
}

::selection {
    background: rgba(79, 195, 247, 0.3);
    color: var(--text);
}

.skip-link {
    position: absolute;
    left: -9999px;
    top: 0;
    z-index: 2000;
    background: var(--accent);
    color: var(--on-accent);
    font-weight: 600;
    padding: 0.6rem 1rem;
    border-radius: 0 0 8px 0;
}

.skip-link:focus { left: 0; }

/* ---------- 3. Utilities ---------- */
.container {
    max-width: var(--max);
    margin: 0 auto;
    padding: 0 var(--space-5);
}

.mono { font-family: var(--font-mono); }

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

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

.section { padding: var(--space-12) 0 var(--space-16); }

main {
    text-align: justify;
    text-justify: inter-word;
}

.section-header,
.hero-grid > div,
.about-text,
.titem,
.portfolio-project,
.skill-cat,
.expertise-card,
.pub-card,
.contact-info,
.contact-form {
    text-align: justify;
    text-justify: inter-word;
}

.section-alt {
    background: var(--bg-soft);
    border-top: 1px solid var(--line);
    border-bottom: 1px solid var(--line);
}

.section-header { margin-bottom: var(--space-8); }

.section-eyebrow {
    display: inline-flex;
    align-items: center;
    gap: 0.65rem;
    font-family: var(--font-mono);
    font-size: var(--text-xs);
    font-weight: 500;
    color: var(--accent);
    letter-spacing: 0.14em;
    text-transform: uppercase;
    margin-bottom: var(--space-3);
}

.section-eyebrow::after {
    content: '';
    width: 48px;
    height: 1px;
    background: linear-gradient(90deg, var(--accent-line), transparent);
}

.section-title {
    font-size: var(--text-2xl);
    font-weight: 800;
}

.section-sub {
    color: var(--muted);
    margin-top: var(--space-3);
    max-width: 62ch;
    font-size: var(--text-md);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.55rem;
    padding: 0.8rem 1.5rem;
    border: none;
    border-radius: 12px;
    font-family: inherit;
    font-weight: 600;
    font-size: 0.95rem;
    text-decoration: none;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease, border-color 0.2s ease;
}

.btn-primary {
    background: var(--gradient);
    color: var(--on-accent);
    box-shadow: var(--glow);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 32px rgba(59, 130, 246, 0.5);
}

.btn-ghost {
    border: 1px solid var(--line-strong);
    color: var(--text);
    background: var(--surface);
}

.btn-ghost:hover {
    background: var(--surface-raised);
    border-color: var(--accent-line);
    transform: translateY(-2px);
}

/* Chips */
.chip {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    font-size: var(--text-xs);
    font-weight: 500;
    color: var(--text);
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--line);
    border-radius: 999px;
    padding: 0.3rem 0.8rem;
    white-space: nowrap;
    transition: border-color 0.2s ease, background 0.2s ease;
}

.chip:hover {
    border-color: var(--accent-line);
    background: var(--accent-soft);
}

.chip img {
    width: 14px;
    height: 14px;
    object-fit: contain;
}

/* Social icon buttons */
.social-link {
    width: 44px;
    height: 44px;
    border-radius: 12px;
    background: #ffffff;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.social-link:hover {
    transform: translateY(-3px);
    box-shadow: var(--glow);
}

.social-link img { width: 22px; height: 22px; }

/* ---------- 4. Navigation ---------- */
.nav {
    position: fixed;
    inset: 0 0 auto 0;
    z-index: 1000;
    background: rgba(8, 12, 30, 0.85);
    -webkit-backdrop-filter: blur(12px);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--line);
}

.nav-progress {
    position: absolute;
    left: 0;
    bottom: -1px;
    height: 2px;
    width: 100%;
    background: var(--brown);
    transform-origin: left;
    transform: scaleX(0);
    pointer-events: none;
}

.nav-inner {
    max-width: var(--max);
    margin: 0 auto;
    height: var(--nav-height);
    padding: 0 var(--space-5);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--space-4);
}

.nav-logo {
    font-weight: 800;
    font-size: 1.3rem;
    color: var(--text);
    text-decoration: none;
    letter-spacing: -0.02em;
    position: relative;
    padding-bottom: 0.1rem;
}

.nav-logo::after {
    content: '';
    position: absolute;
    left: -3px;
    bottom: 1px;
    width: calc(100% + 6px);
    height: 3px;
    background: var(--brown);
    border-radius: 2px;
}

.nav-logo span { color: var(--brown); }

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--space-2);
    align-items: center;
}

.nav-link {
    position: relative;
    display: inline-block;
    color: #ffffff;
    text-decoration: none;
    font-weight: 500;
    font-size: var(--text-sm);
    padding: 0.4rem 0.7rem;
    border-radius: 8px;
    transition: color 0.2s ease;
}

.nav-link::after {
    content: '';
    position: absolute;
    left: 0.7rem;
    right: 0.7rem;
    bottom: 0.1rem;
    height: 2px;
    border-radius: 2px;
    background: var(--brown);
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.25s ease;
}

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

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

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

.nav-toggle {
    display: none;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 10px;
    padding: 0.55rem 0.65rem;
    cursor: pointer;
}

.nav-toggle .bar {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--text);
    margin: 4px 0;
    border-radius: 2px;
    transition: transform 0.25s ease, opacity 0.25s ease;
}

.nav-toggle[aria-expanded="true"] .bar:nth-child(1) { transform: translateY(6px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .bar:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .bar:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

/* ---------- 5. Hero & metrics ---------- */
.hero {
    padding: calc(var(--nav-height) + var(--space-10)) 0 var(--space-10);
    position: relative;
}

.hero-grid {
    display: grid;
    grid-template-columns: 1.25fr 0.75fr;
    gap: var(--space-8);
    align-items: center;
    overflow: hidden;
}

.hero-content {
    transform: translateX(-100%);
    animation: slideInFromLeft 1.7s forwards;
}

.hero-image {
    transform: translateX(100%);
    animation: slideInFromRight 1.7s forwards;
}

@keyframes slideInFromLeft {
    to { transform: translateX(0); }
}

@keyframes slideInFromRight {
    to { transform: translateX(0); }
}

.hero h1 {
    font-size: var(--text-hero);
    font-weight: 800;
    line-height: 1.08;
    margin-bottom: var(--space-4);
}

.hero-role {
    font-size: clamp(1.05rem, 2.2vw, 1.3rem);
    font-weight: 600;
    color: var(--accent);
    margin-bottom: var(--space-4);
    min-height: 1.9rem;
    text-decoration: underline;
    text-decoration-thickness: 2px;
    text-underline-offset: 0.25rem;
}

.typing::after {
    content: '|';
    animation: blink 1s step-end infinite;
    margin-left: 0.15rem;
    color: var(--accent);
}

@keyframes blink {
    0%, 50% { opacity: 1; }
    51%, 100% { opacity: 0; }
}

.hero-pitch {
    font-size: var(--text-md);
    color: var(--muted);
    max-width: 56ch;
    margin-bottom: var(--space-6);
}

.hero-pitch strong { color: var(--text); }

.hero-actions {
    display: flex;
    gap: var(--space-3);
    flex-wrap: wrap;
    margin-bottom: var(--space-5);
}

.hero-socials {
    display: flex;
    gap: var(--space-3);
}

.hero-photo {
    position: relative;
    justify-self: center;
    max-width: 380px;
    width: 100%;
}

.hero-photo::before {
    content: '';
    position: absolute;
    inset: -18px;
    border-radius: 30px;
    background: var(--gradient);
    opacity: 0.22;
    filter: blur(30px);
    z-index: 0;
}

.hero-photo::after {
    content: '';
    position: absolute;
    inset: -1px;
    border-radius: var(--radius-lg);
    padding: 1px;
    background: linear-gradient(160deg, rgba(79, 195, 247, 0.5), rgba(59, 130, 246, 0.05) 45%, rgba(79, 195, 247, 0.25));
    -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
    mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
    -webkit-mask-composite: xor;
    mask-composite: exclude;
    pointer-events: none;
    z-index: 2;
}

.hero-photo img {
    position: relative;
    z-index: 1;
    width: 100%;
    aspect-ratio: 4 / 5;
    max-height: 520px;
    object-fit: cover;
    object-position: center top;
    border-radius: var(--radius-lg);
    display: block;
}

/* Metrics bar */
.stats {
    margin-top: var(--space-10);
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    overflow: hidden;
    transform: translateY(100%);
    animation: slideInFromBottom 1.1s forwards;
}

@keyframes slideInFromBottom {
    to { transform: translateY(0); }
}

.stat {
    padding: var(--space-5) var(--space-4);
    text-align: center;
    position: relative;
}

.stat + .stat::before {
    content: '';
    position: absolute;
    left: 0;
    top: 20%;
    bottom: 20%;
    width: 1px;
    background: var(--line);
}

.stat-value {
    font-family: var(--font-mono);
    font-size: clamp(1.5rem, 3vw, 2.1rem);
    font-weight: 600;
    background: var(--gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    color: transparent;
}

.stat-label {
    font-size: 0.85rem;
    color: var(--muted);
    margin-top: var(--space-1);
}

/* ---------- 6. About ---------- */
.about-grid {
    display: grid;
    grid-template-columns: 1.15fr 0.85fr;
    gap: var(--space-8);
    align-items: stretch;
}

.about-text p {
    color: var(--muted);
    margin-bottom: var(--space-4);
    font-size: var(--text-md);
}

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

.about-focus {
    margin-top: var(--space-5);
    background: var(--surface);
    border: 1px solid var(--line);
    border-left: 3px solid var(--accent);
    border-radius: var(--radius-sm);
    padding: var(--space-4) var(--space-5);
    color: var(--muted);
}

.about-focus strong { color: var(--text); }

.about-gallery {
    position: relative;
    border-radius: var(--radius);
    overflow: hidden;
    height: 100%;
    min-height: 460px;
    max-height: 560px;
    border: 1px solid var(--line);
    box-shadow: var(--shadow-md);
}

.gallery-image {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    opacity: 0;
    transition: opacity 0.8s ease-in-out;
}

.gallery-image.active { opacity: 1; }

.gallery-dots {
    position: absolute;
    left: 0;
    right: 0;
    bottom: var(--space-3);
    display: flex;
    justify-content: center;
    gap: 0.45rem;
    z-index: 2;
}

.gallery-dot {
    width: 8px;
    height: 8px;
    border-radius: 999px;
    border: none;
    background: rgba(255, 255, 255, 0.45);
    cursor: pointer;
    padding: 0;
    transition: background 0.25s ease, width 0.25s ease;
}

.gallery-dot.active {
    width: 22px;
    background: var(--accent);
}

/* ---------- 7. Timeline (Experience / Education) ---------- */
.timeline {
    position: relative;
    padding-left: var(--space-7);
}

.timeline::before {
    content: '';
    position: absolute;
    left: 6px;
    top: 8px;
    bottom: 8px;
    width: 2px;
    background: linear-gradient(to bottom, var(--accent), rgba(79, 195, 247, 0.05));
}

.titem {
    position: relative;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: var(--space-6);
    margin-bottom: var(--space-5);
    transition: transform 0.3s ease, background 0.3s ease, box-shadow 0.3s ease, border-color 0.3s ease;
}

.titem:hover {
    background: var(--surface-raised);
    border-color: var(--accent-line);
    transform: translateX(4px);
    box-shadow: var(--shadow-md);
}

.titem::before {
    content: '';
    position: absolute;
    left: calc(-1 * var(--space-7) + 7px);
    top: 2.1rem;
    width: 13px;
    height: 13px;
    border-radius: 50%;
    background: var(--bg);
    border: 3px solid var(--accent);
    box-shadow: 0 0 0 4px rgba(79, 195, 247, 0.15), 0 0 14px rgba(79, 195, 247, 0.45);
    transform: translateX(-50%);
}

.titem-head {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    grid-template-areas:
        "title date"
        "org location";
    column-gap: var(--space-4);
    row-gap: 0.1rem;
    align-items: start;
    margin-bottom: var(--space-1);
}

.titem-title {
    grid-area: title;
    font-size: var(--text-lg);
    font-weight: 700;
    margin: 0;
}

.titem-date {
    grid-area: date;
    font-family: var(--font-mono);
    font-size: var(--text-xs);
    color: var(--text);
    white-space: nowrap;
    text-align: right;
    padding-top: 0.3rem;
}

.titem-location {
    grid-area: location;
    font-size: var(--text-xs);
    color: var(--text);
    white-space: nowrap;
    text-align: right;
}

.titem-org {
    grid-area: org;
    font-weight: 600;
    color: var(--text);
    margin: 0;
}

.titem-org a {
    color: var(--text);
    text-decoration: none;
    border-bottom: 1px dashed var(--line-strong);
    transition: color 0.2s ease, border-color 0.2s ease;
}

.titem-org a:hover { color: var(--accent); border-bottom-color: var(--accent); }

.titem-meta {
    display: inline-block;
    font-size: var(--text-xs);
    font-weight: 500;
    color: var(--accent);
    background: var(--accent-soft);
    border: 1px solid var(--accent-line);
    border-radius: 999px;
    padding: 0.15rem 0.75rem;
    margin: var(--space-2) 0 var(--space-4);
}

.titem ul {
    list-style: none;
    color: var(--muted);
    display: grid;
    gap: var(--space-2);
}

.titem ul li {
    position: relative;
    padding-left: 1.3rem;
}

.titem ul li::before {
    content: '▹';
    position: absolute;
    left: 0;
    color: var(--accent);
}

.titem ul li strong { color: var(--text); }

.titem .stack-box { margin-top: var(--space-4); }

/* Subtle background image variants */
.titem.has-bg::after {
    content: '';
    position: absolute;
    inset: 0;
    z-index: 0;
    border-radius: inherit;
    opacity: 0.09;
    background-position: center;
    background-size: cover;
    background-repeat: no-repeat;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

.titem.has-bg:hover::after { opacity: 0.14; }

.titem.has-bg > * {
    position: relative;
    z-index: 1;
}

.titem.has-bg.polimi::after { background-image: url('../images/polimibackground.png'); }
.titem.has-bg.hacettepe::after { background-image: url('../images/h1.jpg'); }
.titem.has-bg.czestochowa::after { background-image: url('../images/Czestochowa Campus.jpg'); }
.titem.has-bg.freelance::after { background-image: url('../images/Freelance Background.jpg'); }
.titem.has-bg.havelsan-big::after { background-image: url('../images/e1.jpg'); }
.titem.has-bg.havelsan-ml::after { background-image: url('../images/a1.jpg'); }
.titem.has-bg.ulak::after { background-image: url('../images/ulak.jpg'); }

/* Education */
.edu-head {
    display: flex;
    align-items: flex-start;
    gap: var(--space-4);
}

.edu-logo {
    width: 58px;
    height: 58px;
    object-fit: contain;
    border-radius: 12px;
    background: rgba(255, 255, 255, 0.94);
    padding: 6px;
    flex-shrink: 0;
    box-shadow: var(--shadow-sm);
}

.edu-body { flex: 1; min-width: 0; }

.edu-desc {
    color: var(--muted);
    margin: var(--space-3) 0 var(--space-4);
}

.edu-desc strong { color: var(--text); }

.edu-coursework { margin-top: var(--space-4); }

.edu-coursework-title {
    font-weight: 600;
    color: var(--text);
}

.edu-coursework-grid {
    margin-top: 0.5rem;
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 0.35rem 0.8rem;
}

.edu-coursework-item {
    position: relative;
    padding-left: 1rem;
    color: var(--muted);
    font-size: 0.92rem;
}

.edu-coursework-item::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--brown);
    font-weight: 700;
}

/* ---------- 8. Projects ---------- */
.portfolio-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-8);
}

.portfolio-project {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    position: relative;
    overflow: hidden;
    transition: transform 0.35s ease, box-shadow 0.35s ease, border-color 0.35s ease;
}

.portfolio-project::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse 70% 60% at 10% 0%, rgba(79, 195, 247, 0.08), transparent 60%);
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.35s ease;
}

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

.portfolio-project:hover::before { opacity: 1; }

.portfolio-topbar {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: var(--space-4);
    position: relative;
    z-index: 2;
    margin-bottom: var(--space-2);
}

.portfolio-heading {
    flex: 1;
    min-width: 0;
}

.portfolio-heading .titem-meta {
    margin: var(--space-2) 0 0;
}

.portfolio-title {
    flex: 1;
    min-width: 0;
    margin: 0;
    font-size: var(--text-xl);
    font-weight: 800;
    line-height: 1.25;
}

.portfolio-title a {
    color: var(--text);
    text-decoration: none;
    transition: color 0.2s ease;
}

.portfolio-title a:hover { color: var(--accent); }

.portfolio-body {
    position: relative;
    z-index: 1;
}

.portfolio-desc {
    color: var(--muted);
    font-size: 0.97rem;
    margin-bottom: var(--space-3);
    line-height: 1.75;
}

.portfolio-desc strong { color: var(--text); }

.portfolio-detail {
    color: var(--faint);
    font-size: 0.93rem;
    margin-bottom: var(--space-4);
    line-height: 1.75;
    padding-left: var(--space-4);
    border-left: 2px solid var(--accent-line);
}

.portfolio-detail strong { color: var(--muted); }

.portfolio-highlights-title {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: var(--space-2);
}

.portfolio-highlights {
    list-style: none;
    display: grid;
    gap: var(--space-2);
    margin-bottom: var(--space-4);
}

.portfolio-highlights li {
    position: relative;
    padding-left: 1.3rem;
    color: var(--muted);
    font-size: var(--text-sm);
}

.portfolio-highlights li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--brown);
    font-weight: 700;
}

.portfolio-highlights strong { color: var(--text); }

.stack-box {
    background: var(--surface-deep);
    border: 1px solid var(--line);
    border-radius: 12px;
    padding: var(--space-4) var(--space-5);
    margin-top: var(--space-2);
}

.stack-box h4 {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: var(--space-3);
}

.stack-list {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
}

/* GitHub CTA */
.portfolio-gh {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.55rem 1.1rem;
    border-radius: 12px;
    background: rgba(255, 255, 255, 0.06);
    border: 1px solid var(--line);
    text-decoration: none;
    color: var(--text);
    font-weight: 600;
    font-size: var(--text-sm);
    flex-shrink: 0;
    transition: transform 0.2s ease, background 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.portfolio-gh img {
    width: 18px;
    height: 18px;
    filter: invert(1);
}

.portfolio-gh span { color: var(--accent); }

.portfolio-gh:hover {
    transform: translateY(-3px);
    background: var(--accent-soft);
    border-color: var(--accent-line);
    box-shadow: var(--glow);
}

/* Showcase: main preview + thumbnails */
.portfolio-showcase-wrap {
    position: relative;
    z-index: 1;
    width: 100%;
    margin-top: var(--space-3);
}

.portfolio-showcase {
    border: 1px solid var(--accent-line);
    border-radius: 14px;
    overflow: hidden;
    background: var(--surface-deep);
    box-shadow: var(--shadow-md);
    aspect-ratio: 16 / 9;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-2);
}

.portfolio-main {
    width: 100%;
    height: 100%;
    object-fit: contain;
    object-position: center;
    transition: opacity 0.3s ease;
}

.portfolio-thumbs {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-3);
    margin-top: var(--space-3);
}

.portfolio-thumb {
    border: 2px solid transparent;
    border-radius: var(--radius-sm);
    overflow: hidden;
    padding: 0;
    cursor: pointer;
    background: var(--surface-deep);
    opacity: 0.65;
    transition: opacity 0.2s ease, border-color 0.2s ease, transform 0.2s ease;
}

.portfolio-thumb:hover,
.portfolio-thumb.active {
    opacity: 1;
    border-color: var(--accent);
    transform: translateY(-2px);
}

.portfolio-thumb img {
    display: block;
    width: 100%;
    aspect-ratio: 16 / 10;
    object-fit: contain;
    object-position: center;
    background: rgba(0, 0, 0, 0.25);
    padding: 0.25rem;
}

.portfolio-thumb-label {
    display: block;
    font-family: var(--font-mono);
    font-size: 0.65rem;
    font-weight: 500;
    color: var(--faint);
    text-align: center;
    padding: 0.4rem 0.25rem;
    border-top: 1px solid var(--line);
}

/* Split layout (text + sticky demo) */
.portfolio-split {
    display: grid;
    grid-template-columns: 1.05fr 0.85fr;
    gap: var(--space-6);
    align-items: start;
    position: relative;
    z-index: 1;
}

.portfolio-demo {
    border: 1px solid var(--accent-line);
    border-radius: 14px;
    overflow: hidden;
    background: var(--surface-deep);
    box-shadow: var(--shadow-md);
    aspect-ratio: 3 / 4;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-3);
    position: sticky;
    top: calc(var(--nav-height) + var(--space-4));
}

.portfolio-demo img {
    width: 100%;
    height: 100%;
    object-fit: contain;
    object-position: center;
    border-radius: 8px;
}

/* GitHub repo strip */
.gh-strip {
    margin-top: var(--space-8);
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: var(--space-4);
}

.gh-card {
    display: block;
    text-decoration: none;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 12px;
    padding: var(--space-4) var(--space-5);
    transition: background 0.2s ease, transform 0.2s ease, border-color 0.2s ease;
}

.gh-card:hover {
    background: var(--surface-raised);
    border-color: var(--accent-line);
    transform: translateY(-3px);
}

.gh-card h4 {
    color: var(--text);
    font-size: 0.98rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: var(--space-1);
}

.gh-card h4 img { width: 16px; height: 16px; filter: invert(1); }

.gh-card p {
    color: var(--faint);
    font-size: 0.85rem;
}

/* ---------- 9. Publication ---------- */
.pub-card {
    background: var(--surface);
    border: 1px solid var(--line);
    border-left: 4px solid var(--accent);
    border-radius: var(--radius);
    padding: var(--space-6) var(--space-7);
    position: relative;
    overflow: hidden;
    transition: border-color 0.3s ease, box-shadow 0.3s ease;
}

.pub-card:hover {
    border-color: var(--accent-line);
    border-left-color: var(--accent);
    box-shadow: var(--shadow-md);
}

.pub-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: url('../images/paper.png') center/cover no-repeat;
    opacity: 0.1;
    z-index: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

.pub-card:hover::before { opacity: 0.16; }

.pub-card > * {
    position: relative;
    z-index: 1;
}

.pub-head {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    grid-template-areas:
        "title date"
        "venue location";
    column-gap: var(--space-4);
    row-gap: 0.15rem;
    align-items: start;
    margin-bottom: var(--space-4);
}

.pub-title {
    grid-area: title;
    font-size: var(--text-xl);
    font-weight: 700;
    margin: 0;
}

.pub-title a {
    color: var(--text);
    text-decoration: none;
    transition: color 0.2s ease;
}

.pub-title a:hover { color: var(--accent); }

.pub-date {
    grid-area: date;
    font-family: var(--font-mono);
    font-size: var(--text-xs);
    color: var(--text);
    white-space: nowrap;
    text-align: right;
    padding-top: 0.3rem;
}

.pub-venue {
    grid-area: venue;
    display: inline-block;
    font-size: var(--text-xs);
    font-weight: 500;
    color: var(--text);
    background: var(--accent-soft);
    border: 1px solid var(--accent-line);
    border-radius: 999px;
    padding: 0.15rem 0.75rem;
    margin: var(--space-2) 0 0;
    width: fit-content;
}

.pub-location {
    grid-area: location;
    font-size: var(--text-xs);
    color: var(--text);
    white-space: nowrap;
    text-align: right;
}

.pub-citation {
    font-family: var(--font-mono);
    font-size: 0.83rem;
    color: var(--faint);
    background: var(--surface-deep);
    border: 1px solid var(--line);
    border-radius: var(--radius-sm);
    padding: var(--space-3) var(--space-4);
    margin-bottom: var(--space-5);
    line-height: 1.7;
}

.pub-citation strong { color: var(--muted); }

.pub-card ul {
    list-style: none;
    color: var(--muted);
    display: grid;
    gap: var(--space-2);
    margin-bottom: var(--space-5);
}

.pub-card ul li {
    position: relative;
    padding-left: 1.3rem;
}

.pub-card ul li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--brown);
    font-weight: 700;
}

.pub-card ul li strong { color: var(--text); }

.pub-links {
    display: flex;
    gap: var(--space-3);
    flex-wrap: wrap;
}

.pub-links a {
    font-size: var(--text-sm);
    font-weight: 600;
    text-decoration: none;
    padding: 0.45rem 1rem;
    border: 1px solid var(--accent-line);
    border-radius: 10px;
    background: var(--accent-soft);
    transition: background 0.2s ease, transform 0.2s ease, box-shadow 0.2s ease;
}

.pub-links a:hover {
    background: rgba(79, 195, 247, 0.2);
    transform: translateY(-2px);
    box-shadow: var(--glow);
}

/* ---------- 10. Skills ---------- */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--space-5);
}

.skill-cat {
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: var(--space-5) var(--space-6);
    transition: border-color 0.25s ease, transform 0.25s ease, background 0.25s ease;
}

.skill-cat:hover {
    border-color: var(--accent-line);
    background: var(--surface-raised);
    transform: translateY(-3px);
}

.skill-cat h3 {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: var(--space-4);
}

.skill-items {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-3);
}

.skill-item {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--line);
    border-radius: var(--radius-sm);
    padding: 0.45rem 0.85rem;
    font-size: 0.88rem;
    font-weight: 500;
    color: var(--text);
    transition: transform 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}

.skill-item:hover {
    transform: translateY(-2px);
    border-color: var(--accent-line);
    background: var(--accent-soft);
}

.skill-item img { width: 20px; height: 20px; object-fit: contain; }

/* Expertise bars */
.expertise-grid {
    display: grid;
    grid-template-columns: minmax(0, 1.15fr) minmax(260px, 0.85fr);
    gap: var(--space-5);
    margin-top: var(--space-6);
}

.expertise-card {
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: var(--space-5) var(--space-6);
}

.expertise-card h3 {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: var(--space-4);
}

.expertise-card p {
    color: var(--muted);
    margin-bottom: var(--space-4);
}

.expertise-card p strong { color: var(--text); }

.skill-bar { margin-bottom: var(--space-4); }

.skill-name {
    display: flex;
    justify-content: space-between;
    gap: var(--space-4);
    color: var(--text);
    font-weight: 600;
    font-size: var(--text-sm);
    margin-bottom: var(--space-2);
}

.skill-level {
    height: 8px;
    background: rgba(255, 255, 255, 0.07);
    border-radius: 999px;
    overflow: hidden;
}

.skill-progress {
    height: 100%;
    width: 0;
    border-radius: inherit;
    background: var(--gradient);
    transition: width 1.2s ease;
}

/* Languages */
.lang-row {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-4);
    margin-top: var(--space-6);
}

.lang-card {
    flex: 1;
    min-width: 200px;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 12px;
    padding: var(--space-4) var(--space-5);
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: border-color 0.2s ease, transform 0.2s ease;
}

.lang-card:hover {
    border-color: var(--accent-line);
    transform: translateY(-2px);
}

.lang-card .name { font-weight: 600; }

.lang-card .level {
    font-family: var(--font-mono);
    font-size: var(--text-xs);
    color: var(--accent);
}

/* ---------- 11. Blog ---------- */
.blog-preview-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--space-5);
}

.blog-preview-card {
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    text-decoration: none;
    color: inherit;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: var(--space-6) var(--space-5);
    position: relative;
    overflow: hidden;
    min-height: 300px;
    box-shadow: var(--shadow-sm);
    transition: transform 0.3s ease, box-shadow 0.3s ease, border-color 0.3s ease;
}

.blog-preview-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background-size: cover;
    background-position: center;
    opacity: 0.34;
    transform: scale(1);
    transition: opacity 0.35s ease, transform 0.6s ease;
}

.blog-preview-card::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(170deg, rgba(4, 8, 18, 0.55), rgba(4, 8, 18, 0.92));
}

.blog-preview-card > * {
    position: relative;
    z-index: 1;
}

.blog-preview-card.article-600tb::before { background-image: url('../images/articles/distributed-systems.jpg'); }
.blog-preview-card.article-k8s::before { background-image: url('../images/articles/kubernetes-platform.jpg'); }
.blog-preview-card.article-observability::before { background-image: url('../images/articles/observability.jpg'); }

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

.blog-preview-card:hover::before {
    opacity: 0.48;
    transform: scale(1.05);
}

.blog-preview-title {
    margin: 0 0 var(--space-2);
    font-size: 1.18rem;
    line-height: 1.4;
    color: var(--text);
}

.blog-preview-meta {
    color: var(--faint);
    font-family: var(--font-mono);
    font-size: var(--text-xs);
    margin-bottom: var(--space-3);
}

.blog-preview-summary {
    margin: 0;
    color: var(--muted);
    font-size: 0.95rem;
    line-height: 1.62;
}

.blog-preview-footer { margin-top: var(--space-6); }

.blog-preview-link {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--accent);
    font-weight: 600;
    text-decoration: none;
    transition: gap 0.2s ease;
}

.blog-preview-link:hover {
    text-decoration: underline;
    gap: 0.65rem;
}

/* ---------- 12. Contact ---------- */
.contact-grid {
    display: grid;
    grid-template-columns: 0.9fr 1.1fr;
    gap: var(--space-5);
    align-items: stretch;
}

.contact-info,
.contact-form {
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: var(--space-7);
}

.contact-info p {
    color: var(--muted);
    margin-bottom: var(--space-5);
}

.contact-block { margin-bottom: var(--space-5); }

.contact-block h3 {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: var(--space-3);
}

.contact-emails {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.contact-emails a {
    font-family: var(--font-mono);
    font-size: var(--text-sm);
    color: var(--accent);
    text-decoration: none;
    overflow-wrap: anywhere;
}

.contact-emails a:hover { text-decoration: underline; }

.contact-socials {
    display: flex;
    gap: var(--space-3);
}

.form-group { margin-bottom: var(--space-4); }

.form-group label {
    display: block;
    color: var(--text);
    font-weight: 600;
    font-size: var(--text-sm);
    margin-bottom: var(--space-2);
}

.form-group input,
.form-group textarea {
    width: 100%;
    border: 1px solid var(--line);
    border-radius: var(--radius-sm);
    background: var(--surface-deep);
    color: var(--text);
    font: inherit;
    padding: 0.85rem 1rem;
    transition: border-color 0.2s ease, background 0.2s ease, box-shadow 0.2s ease;
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--accent);
    background: rgba(2, 6, 18, 0.65);
    box-shadow: 0 0 0 3px rgba(79, 195, 247, 0.15);
}

.form-group textarea {
    min-height: 140px;
    resize: vertical;
}

/* ---------- 13. Footer ---------- */
.footer {
    border-top: 1px solid var(--line);
    padding: var(--space-6) var(--space-5);
    text-align: center;
    color: var(--faint);
    font-size: var(--text-sm);
}

.footer a { color: var(--muted); text-decoration: none; }

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

.footer .copyright-text {
    color: var(--text);
    font-weight: 700;
}

/* ---------- 14. Motion ---------- */
.fade-in {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.6s ease;
}

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

/* ---------- 15. Responsive ---------- */
@media (max-width: 960px) {
    .hero-grid { grid-template-columns: 1fr; gap: var(--space-7); }
    .hero-photo { max-width: 300px; order: -1; }
    .stats { grid-template-columns: repeat(2, 1fr); }
    .stat:nth-child(odd)::before { display: none; }
    .stat:nth-child(n+3) { border-top: 1px solid var(--line); }
    .about-grid { grid-template-columns: 1fr; }
    .about-gallery { max-height: 420px; }
    .portfolio-split { grid-template-columns: 1fr; }
    .portfolio-demo { position: static; max-width: 360px; margin: 0 auto; width: 100%; }
    .expertise-grid { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
    .section { padding: var(--space-10) 0 var(--space-12); }

    .nav-toggle { display: block; }

    .nav-menu {
        position: fixed;
        top: var(--nav-height);
        left: 0;
        right: 0;
        bottom: 0;
        flex-direction: column;
        align-items: stretch;
        justify-content: flex-start;
        gap: 0;
        background: rgba(4, 7, 18, 0.96);
        -webkit-backdrop-filter: blur(20px);
        backdrop-filter: blur(20px);
        padding: var(--space-5) 0 var(--space-8);
        overflow-y: auto;
        visibility: hidden;
        opacity: 0;
        transform: translateY(-8px);
        transition: opacity 0.25s ease, transform 0.25s ease, visibility 0.25s;
    }

    .nav-menu.open {
        visibility: visible;
        opacity: 1;
        transform: translateY(0);
    }

    .nav-menu li {
        text-align: center;
        opacity: 0;
        transform: translateY(10px);
        transition: opacity 0.3s ease, transform 0.3s ease;
    }

    .nav-menu.open li {
        opacity: 1;
        transform: translateY(0);
    }

    .nav-menu.open li:nth-child(1) { transition-delay: 0.04s; }
    .nav-menu.open li:nth-child(2) { transition-delay: 0.08s; }
    .nav-menu.open li:nth-child(3) { transition-delay: 0.12s; }
    .nav-menu.open li:nth-child(4) { transition-delay: 0.16s; }
    .nav-menu.open li:nth-child(5) { transition-delay: 0.2s; }
    .nav-menu.open li:nth-child(6) { transition-delay: 0.24s; }
    .nav-menu.open li:nth-child(7) { transition-delay: 0.28s; }
    .nav-menu.open li:nth-child(8) { transition-delay: 0.32s; }
    .nav-menu.open li:nth-child(9) { transition-delay: 0.36s; }

    .nav-link {
        display: block;
        padding: 0.9rem 1.5rem;
        font-size: 1.05rem;
    }

    .nav-link::after { display: none; }

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

    .titem { padding: var(--space-5); }
    .titem-head {
        grid-template-columns: 1fr;
        grid-template-areas:
            "title"
            "org"
            "date"
            "location";
    }
    .titem-date, .titem-location { text-align: left; padding-top: 0; }

    .pub-head {
        grid-template-columns: 1fr;
        grid-template-areas:
            "title"
            "venue"
            "date"
            "location";
    }
    .pub-date, .pub-location { text-align: left; padding-top: 0; }
    .pub-card { padding: var(--space-5); }

    .portfolio-project { padding: var(--space-5); }
    .portfolio-topbar { flex-direction: column; align-items: flex-start; }
    .contact-grid { grid-template-columns: 1fr; }
    .contact-info, .contact-form { padding: var(--space-5); }
    .edu-head { flex-direction: column; }
    .edu-coursework-grid { grid-template-columns: 1fr; }
}

@media (max-width: 600px) {
    .portfolio-thumbs { grid-template-columns: repeat(2, 1fr); }
    .stats { grid-template-columns: 1fr 1fr; }
}

/* ---------- Reduced motion (minimal, matches old index) ---------- */
@media (prefers-reduced-motion: reduce) {
    .portfolio-project:hover { transform: none; }
    .portfolio-thumb:hover { transform: none; }
    .portfolio-main { transition: none; }
}