:root {
    --bg: #f6f8fb;
    --surface: #ffffff;
    --surface-strong: #111827;
    --text: #172033;
    --muted: #617087;
    --line: #dbe3ee;
    --teal: #0f766e;
    --teal-dark: #115e59;
    --blue: #2563eb;
    --amber: #f59e0b;
    --shadow: 0 24px 70px rgba(23, 32, 51, 0.12);
    --radius: 8px;
    --max-width: 1180px;
}

* {
    box-sizing: border-box;
}

/* Enable smooth scrolling for anchor links. */
html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    background:
        radial-gradient(circle at top left, rgba(15, 118, 110, 0.12), transparent 32rem),
        linear-gradient(180deg, #ffffff 0%, var(--bg) 34%, #eef4f8 100%);
    color: var(--text);
    font-family: "Inter", Arial, sans-serif;
    line-height: 1.6;
}

/* Prevents scrolling on the body when the mobile menu is open. */
body.menu-open {
    overflow: hidden;
}

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

a {
    color: inherit;
}

/* Header & Navigation*/

.site-header {
    position: sticky;
    top: 0;
    z-index: 20;
    border-bottom: 1px solid rgba(219, 227, 238, 0.9);
    background: rgba(255, 255, 255, 0.84);
    backdrop-filter: blur(18px);
}

/* The main container for the navigation, centered with a max-width. */
.nav-shell {
    width: min(var(--max-width), calc(100% - 40px));
    min-height: 76px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

/* The site logo/brand link in the top-left. */
.brand {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    color: var(--surface-strong);
    font-weight: 800;
    text-decoration: none;
}

/* The "SK" mark inside the brand, with a fun shadow effect. */
.brand-mark {
    width: 44px;
    height: 44px;
    display: grid;
    place-items: center;
    border-radius: var(--radius);
    background: var(--surface-strong);
    color: #ffffff;
    font-family: "JetBrains Mono", monospace;
    font-size: 0.92rem;
    box-shadow: 8px 8px 0 rgba(15, 118, 110, 0.18);
}

.brand-text {
    letter-spacing: 0;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 6px;
    margin: 0;
    padding: 0;
    list-style: none;
}

/* Individual navigation links with hover/active states. */
.nav-links a {
    display: inline-flex;
    align-items: center;
    min-height: 40px;
    padding: 0 14px;
    border-radius: var(--radius);
    color: var(--muted);
    font-size: 0.95rem;
    font-weight: 700;
    text-decoration: none;
    transition: color 180ms ease, background-color 180ms ease;
}

.nav-links a:hover,
.nav-links a.active {
    background: rgba(15, 118, 110, 0.09);
    color: var(--teal-dark);
}

/* The hamburger menu button, hidden on desktop. */
.nav-toggle {
    display: none;
    width: 44px;
    height: 44px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--surface);
    color: var(--surface-strong);
    cursor: pointer;
    font-size: 1.1rem;
}

/* Layout & Content Sections */

.section-block {
    width: min(var(--max-width), calc(100% - 40px));
    margin: 0 auto;
    padding: 92px 0;
}

.hero {
    min-height: calc(100vh - 76px);
    display: grid;
    grid-template-columns: minmax(0, 1.15fr) minmax(320px, 0.85fr);
    align-items: center;
    gap: 64px;
    padding-top: 54px;
}

.eyebrow {
    margin: 0 0 14px;
    color: var(--teal);
    font-family: "JetBrains Mono", monospace;
    font-size: 0.78rem;
    font-weight: 700;
    text-transform: uppercase;
}

h1, h2, h3, p {
    margin-top: 0;
}

h1 {
    max-width: 780px;
    margin-bottom: 24px;
    color: var(--surface-strong);
    font-size: clamp(2.8rem, 8vw, 5.9rem);
    line-height: 0.98;
    letter-spacing: 0;
}

h2 {
    max-width: 770px;
    margin-bottom: 0;
    color: var(--surface-strong);
    font-size: clamp(2rem, 4vw, 3.5rem);
    line-height: 1.05;
    letter-spacing: 0;
}

h3 {
    margin-bottom: 8px;
    color: var(--surface-strong);
    font-size: 1.1rem;
    line-height: 1.2;
}

.hero-summary {
    max-width: 660px;
    margin-bottom: 30px;
    color: var(--muted);
    font-size: 1.16rem;
}

.professional-tagline {
    max-width: 730px;
    margin-bottom: 18px;
    color: var(--surface-strong);
    font-size: 0.98rem;
    font-weight: 800;
}

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

/* Base styles for all buttons. */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 48px;
    gap: 10px;
    padding: 0 18px;
    border: 1px solid transparent;
    border-radius: var(--radius);
    font-weight: 800;
    text-decoration: none;
    transition: transform 180ms ease, box-shadow 180ms ease, background-color 180ms ease, color 180ms ease;
}

.btn:hover {
    transform: translateY(-2px);
}

/* Primary button style (dark background, light text). */
.btn.primary {
    background: var(--surface-strong);
    color: #ffffff;
    box-shadow: 0 14px 28px rgba(17, 24, 39, 0.18);
}

.btn.primary:hover {
    background: var(--teal-dark);
}

/* Secondary button style (light background, dark text, with a border). */
.btn.secondary {
    border-color: var(--line);
    background: var(--surface);
    color: var(--surface-strong);
}

.btn.secondary:hover {
    border-color: rgba(37, 99, 235, 0.35);
    color: var(--blue);
    box-shadow: 0 14px 30px rgba(37, 99, 235, 0.1);
}

.brand:focus-visible,
.nav-links a:focus-visible,
.nav-toggle:focus-visible,
.btn:focus-visible,
.contact-actions a:focus-visible,
.visitor-counter:focus-visible {
    outline: 3px solid rgba(245, 158, 11, 0.72);
    outline-offset: 4px;
}

.signal-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 12px;
    margin-top: 38px;
}

.signal-grid div {
    min-height: 96px;
    padding: 18px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: rgba(255, 255, 255, 0.78);
}

/* Shared style for small, uppercase text labels. */
.signal-grid span,
.project-meta span,
.panel-kicker,
.timeline-date {
    display: block;
    margin-bottom: 6px;
    color: var(--muted);
    font-family: "JetBrains Mono", monospace;
    font-size: 0.76rem;
    font-weight: 700;
    text-transform: uppercase;
}

.signal-grid strong {
    color: var(--surface-strong);
    font-size: 1rem;
}

.hero-visual {
    position: relative;
}

/* The frame around the portrait image, with a subtle gradient and shadow. */
.portrait-frame {
    position: relative;
    overflow: hidden;
    border: 1px solid rgba(17, 24, 39, 0.1);
    border-radius: var(--radius);
    background: linear-gradient(145deg, #111827, #1f2937);
    box-shadow: var(--shadow);
}

/* An inset border effect inside the portrait frame. */
.portrait-frame::before {
    content: "";
    position: absolute;
    inset: 18px;
    border: 1px solid rgba(255, 255, 255, 0.16);
    border-radius: var(--radius);
    pointer-events: none;
}

.portrait-frame img {
    width: 100%;
    aspect-ratio: 4 / 5;
    object-fit: cover;
    object-position: 50% 30%;
}

/* The small panel that overlays the portrait, with the rotating text. */
.focus-panel {
    position: absolute;
    right: -24px;
    bottom: 28px;
    width: min(285px, 78%);
    padding: 18px;
    border: 1px solid rgba(219, 227, 238, 0.9);
    border-radius: var(--radius);
    background: rgba(255, 255, 255, 0.95);
    box-shadow: 0 18px 42px rgba(23, 32, 51, 0.16);
}

.focus-panel strong {
    display: block;
    min-height: 29px;
    color: var(--surface-strong);
    font-size: 1.05rem;
}

/* The heading block for each major section. */
.section-heading {
    display: grid;
    grid-template-columns: 0.42fr 1fr;
    align-items: start;
    gap: 42px;
    margin-bottom: 38px;
}

/* Modifier classes for different heading layouts. */
.section-heading.compact,
.section-heading.centered {
    display: block;
}

.section-heading.centered {
    max-width: 720px;
    margin-right: auto;
    margin-left: auto;
    text-align: center;
}

.section-heading.centered p:not(.eyebrow) {
    margin-top: 18px;
    color: var(--muted);
}

.about-layout {
    display: grid;
    grid-template-columns: 0.88fr 1.12fr;
    gap: 26px;
    align-items: start;
}

/* The main text block in the "About" section. */
.about-copy {
    padding: 28px;
    border-left: 4px solid var(--teal);
    background: rgba(255, 255, 255, 0.72);
}

.about-copy p {
    color: var(--muted);
    font-size: 1.04rem;
}

.about-copy p:last-child,
.principles p,
.timeline-item p,
.project-card p,
.resume-band p,
.site-footer p {
    margin-bottom: 0;
}

/* The 3-column grid for the "Backend Thinking," "Security," and "AI" principles. */
.principles {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
}

/* Base card style used for principles, skills, and projects. */
.principles article,
.skill-card,
.project-card {
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--surface);
    box-shadow: 0 16px 42px rgba(23, 32, 51, 0.07);
}

.principles article {
    min-height: 225px;
    padding: 24px;
}

/* The icon styling within the principle cards. */
.principles i {
    width: 42px;
    height: 42px;
    display: grid;
    place-items: center;
    margin-bottom: 18px;
    border-radius: var(--radius);
    background: rgba(15, 118, 110, 0.1);
    color: var(--teal);
    font-size: 1rem;
}

.principles p,
.timeline-item p,
.project-card p {
    color: var(--muted);
}

/* The grid that holds all the skill cards. */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 14px;
    margin-top: 34px;
}

.skill-card {
    padding: 24px;
}

/* A list of pill-shaped tags, used for skills and project technologies. */
.pill-list,
.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin: 0;
    padding: 0;
    list-style: none;
}

.pill-list li,
.project-tags li {
    min-height: 34px;
    display: inline-flex;
    align-items: center;
    border-radius: 999px;
    font-size: 0.88rem;
    font-weight: 800;
}

.pill-list li {
    padding: 0 12px;
    background: #eef7f6;
    color: var(--teal-dark);
}

/* The container for the experience timeline. */
.timeline {
    display: grid;
    gap: 18px;
}

/* A single item in the experience timeline. */
.timeline-item {
    display: grid;
    grid-template-columns: 180px minmax(0, 1fr);
    gap: 28px;
    padding: 28px;
    border-left: 4px solid var(--surface-strong);
    background: rgba(255, 255, 255, 0.78);
}

.timeline-date {
    color: var(--teal-dark);
}

.timeline-place {
    margin-bottom: 10px;
    color: var(--blue);
    font-weight: 800;
}

/* The main project card style. */
.project-card {
    padding: clamp(24px, 4vw, 42px);
}

.project-meta {
    display: flex;
    align-items: end;
    justify-content: space-between;
    gap: 18px;
    margin-bottom: 18px;
}

.project-meta h3 {
    margin-bottom: 0;
    font-size: clamp(1.8rem, 4vw, 3rem);
}

.project-tags {
    margin: 24px 0 28px;
}

.project-tags li {
    padding: 0 13px;
    background: #eff6ff;
    color: #1d4ed8;
}

/* The full-width "Resume" call-to-action band. */
.resume-band {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 28px;
    padding: clamp(28px, 5vw, 54px);
    border-radius: var(--radius);
    background:
        linear-gradient(135deg, rgba(15, 118, 110, 0.94), rgba(17, 24, 39, 0.96)),
        var(--surface-strong);
    color: #ffffff;
}

.resume-band h2,
.resume-band .eyebrow {
    color: #ffffff;
}

.resume-band p {
    max-width: 670px;
    color: rgba(255, 255, 255, 0.78);
}

.resume-band .btn.primary {
    flex: 0 0 auto;
    background: #ffffff;
    color: var(--surface-strong);
}

.resume-band .btn.primary:hover {
    background: #fff8e7;
}

/* The final "Contact" section. */
.contact-section {
    padding-bottom: 70px;
}

.contact-actions {
    /* A responsive grid for all the social/contact links. */
    display: grid;
    grid-template-columns: repeat(6, minmax(0, 1fr));
    gap: 12px;
}

.contact-actions a {
    min-height: 110px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 10px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--surface);
    color: var(--surface-strong);
    font-weight: 800;
    text-decoration: none;
    transition: transform 180ms ease, border-color 180ms ease, color 180ms ease, box-shadow 180ms ease;
}

.contact-actions a:hover {
    transform: translateY(-3px);
    border-color: rgba(15, 118, 110, 0.35);
    color: var(--teal-dark);
    box-shadow: 0 18px 38px rgba(15, 118, 110, 0.12);
}

.contact-actions i {
    font-size: 1.6rem;
}

/* The site footer at the very bottom of the page. */
.site-footer {
    width: min(var(--max-width), calc(100% - 40px));
    margin: 0 auto;
    padding: 30px 0 38px;
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    align-items: center;
    gap: 20px;
    border-top: 1px solid var(--line);
    color: var(--muted);
    font-size: 0.92rem;
}

.site-footer div {
    display: grid;
    gap: 2px;
}

.site-footer strong {
    color: var(--surface-strong);
}

.site-footer p {
    text-align: right;
}

.visitor-counter {
    display: inline-flex;
    justify-self: center;
    min-height: 28px;
}

.visitor-counter img {
    height: 28px;
}

@media (max-width: 1040px) {
    .hero,
    .about-layout,
    .section-heading {
        grid-template-columns: 1fr;
    }

    .hero {
        min-height: auto;
        gap: 42px;
        padding-top: 60px;
    }

    .hero-visual {
        max-width: 520px;
    }

    .principles,
    .skills-grid,
    .contact-actions {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

/* On smaller tablets and mobile devices, we switch to a mobile-friendly navigation. */
@media (max-width: 760px) {
    .nav-shell,
    .section-block,
    .site-footer {
        width: min(100% - 28px, var(--max-width));
    }

    .nav-toggle {
        display: grid;
        place-items: center;
    }

    /* The mobile navigation menu appears as an overlay. */
    .nav-links {
        position: fixed;
        inset: 76px 14px auto 14px;
        display: grid;
        gap: 8px;
        padding: 14px;
        border: 1px solid var(--line);
        border-radius: var(--radius);
        background: rgba(255, 255, 255, 0.98);
        box-shadow: var(--shadow);
        transform: translateY(-16px);
        opacity: 0;
        pointer-events: none;
        transition: opacity 180ms ease, transform 180ms ease;
    }

    /* The ".open" class is toggled by JavaScript to show/hide the menu. */
    .nav-links.open {
        transform: translateY(0);
        opacity: 1;
        pointer-events: auto;
    }

    .nav-links a {
        width: 100%;
        justify-content: center;
    }

    .section-block {
        padding: 66px 0;
    }

    .hero {
        padding-top: 42px;
    }

    h1 {
        font-size: clamp(2.6rem, 14vw, 4rem);
    }

    .hero-summary {
        font-size: 1rem;
    }

    .signal-grid,
    .principles,
    .skills-grid,
    .contact-actions {
        grid-template-columns: 1fr;
    }

    /* The focus panel is no longer an overlay on mobile; it sits below the image. */
    .focus-panel {
        position: static;
        width: 100%;
        margin-top: 12px;
    }

    .timeline-item {
        grid-template-columns: 1fr;
        gap: 12px;
    }

    .project-meta,
    .resume-band,
    .site-footer {
        display: grid;
        grid-template-columns: 1fr;
    }

    .resume-band .btn.primary {
        width: 100%;
    }

    .site-footer,
    .site-footer p {
        text-align: center;
    }
}

/* On very small screens, make some final adjustments for readability. */
@media (max-width: 460px) {
    .brand-text {
        display: none;
    }

    .hero-actions,
    .project-actions {
        display: grid;
    }

    .btn {
        width: 100%;
    }

    .about-copy,
    .principles article,
    .skill-card,
    .timeline-item,
    .project-card {
        padding: 22px;
    }
}