/* ═══════════════════════════════════════════════
   Quantum Light — Dark theme
   bg: deep charcoal · accent: amber · teal secondary
   ═══════════════════════════════════════════════ */

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* ── Core palette ── */
    --color-bg:            #0f1117;
    --color-surface:       #161b27;
    --color-surface-alt:   #1e2535;
    --color-surface-raise: #242d3e;

    /* ── Borders ── */
    --color-border:        #2a3347;
    --color-border-light:  #1e2840;

    /* ── Text ── */
    --color-text:          #f1f5f9;
    --color-text-secondary:#94a3b8;
    --color-text-muted:    #64748b;

    /* ── Amber accent (primary / science warmth) ── */
    --color-accent:        #f59e0b;
    --color-accent-hover:  #d97706;
    --color-accent-light:  rgba(245, 158, 11, 0.12);
    --color-accent-lighter:rgba(245, 158, 11, 0.06);

    /* ── Teal accent (secondary / tech / quantum) ── */
    --color-teal:          #2dd4bf;
    --color-teal-hover:    #14b8a6;
    --color-teal-light:    rgba(45, 212, 191, 0.12);

    /* ── Success / other ── */
    --color-success:       #34d399;

    /* ── Typography ── */
    --font-family: -apple-system, "Segoe UI", "Helvetica Neue", sans-serif;
    --font-mono:   "SF Mono", Monaco, "Cascadia Code", "Roboto Mono", Consolas, monospace;

    /* ── Spacing ── */
    --spacing-xs:  0.5rem;
    --spacing-sm:  1rem;
    --spacing-md:  1.5rem;
    --spacing-lg:  2rem;
    --spacing-xl:  3rem;
    --spacing-2xl: 4rem;
    --spacing-3xl: 6rem;

    /* ── Shadows (dark-mode: glow-tinted) ── */
    --shadow-sm:  0 1px 3px rgba(0,0,0,0.4);
    --shadow-md:  0 4px 12px rgba(0,0,0,0.5);
    --shadow-lg:  0 10px 30px rgba(0,0,0,0.6);
    --shadow-xl:  0 20px 50px rgba(0,0,0,0.7);
    --glow-amber: 0 0 20px rgba(245, 158, 11, 0.25);
    --glow-teal:  0 0 20px rgba(45, 212, 191, 0.25);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.65;
    font-size: 15px;
}

.container {
    max-width: 760px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ══════════════════════════════
   Navigation
══════════════════════════════ */
.navbar {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: rgba(15, 17, 23, 0.85);
    border-bottom: 1px solid var(--color-border);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
}

.nav-container {
    max-width: 760px;
    margin: 0 auto;
    padding: var(--spacing-md) var(--spacing-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 700;
    font-size: 18px;
    color: var(--color-text);
    text-decoration: none;
    letter-spacing: -0.5px;
    transition: color 0.2s ease;
}

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

.logo-avatar {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    object-fit: cover;
    object-position: top center;
    border: 2px solid var(--color-border);
    transition: border-color 0.2s ease;
    flex-shrink: 0;
}

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

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-lg);
}

.nav-menu a {
    color: var(--color-text-secondary);
    text-decoration: none;
    font-size: 13px;
    font-weight: 500;
    transition: color 0.2s ease;
}

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

/* Hamburger — hidden on desktop */
.nav-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    color: var(--color-text);
    line-height: 0;
}

.nav-toggle svg {
    display: block;
}

/* ══════════════════════════════
   Hero — Starfield
══════════════════════════════ */
.hero {
    position: relative;
    overflow: hidden;
    padding: var(--spacing-3xl) var(--spacing-md) var(--spacing-2xl);
    text-align: center;
    background-color: var(--color-bg);
}

/* Starfield — two layers of CSS radial dots */
.hero::before,
.hero::after {
    content: '';
    position: absolute;
    inset: 0;
    pointer-events: none;
}

.hero::before {
    background-image:
        radial-gradient(1px 1px at 10%  15%, rgba(241,245,249,0.55) 0%, transparent 100%),
        radial-gradient(1px 1px at 25%  60%, rgba(241,245,249,0.40) 0%, transparent 100%),
        radial-gradient(1px 1px at 40%  30%, rgba(241,245,249,0.50) 0%, transparent 100%),
        radial-gradient(1px 1px at 55%  75%, rgba(241,245,249,0.35) 0%, transparent 100%),
        radial-gradient(1px 1px at 70%  20%, rgba(241,245,249,0.60) 0%, transparent 100%),
        radial-gradient(1px 1px at 82%  50%, rgba(241,245,249,0.45) 0%, transparent 100%),
        radial-gradient(1px 1px at 92%  10%, rgba(241,245,249,0.55) 0%, transparent 100%),
        radial-gradient(1px 1px at  5%  80%, rgba(241,245,249,0.30) 0%, transparent 100%),
        radial-gradient(1px 1px at 60%  90%, rgba(241,245,249,0.40) 0%, transparent 100%),
        radial-gradient(1px 1px at 33%  42%, rgba(241,245,249,0.50) 0%, transparent 100%),
        radial-gradient(1px 1px at 75%  68%, rgba(241,245,249,0.35) 0%, transparent 100%),
        radial-gradient(1px 1px at 88%  85%, rgba(241,245,249,0.45) 0%, transparent 100%),
        radial-gradient(2px 2px at 18%  35%, rgba(45,212,191,0.30)  0%, transparent 100%),
        radial-gradient(2px 2px at 67%  12%, rgba(245,158,11,0.25)  0%, transparent 100%),
        radial-gradient(2px 2px at 48%  55%, rgba(45,212,191,0.20)  0%, transparent 100%),
        radial-gradient(2px 2px at 90%  40%, rgba(245,158,11,0.20)  0%, transparent 100%);
    opacity: 0.9;
}

/* Ambient glow blobs */
.hero::after {
    background:
        radial-gradient(ellipse 600px 300px at 80% 50%, rgba(245,158,11,0.05) 0%, transparent 70%),
        radial-gradient(ellipse 500px 250px at 15% 40%, rgba(45,212,191,0.05) 0%, transparent 70%);
}

.hero-content {
    max-width: 700px;
    margin: 0 auto;
    position: relative;
    z-index: 1;
}

.hero h1 {
    font-size: 56px;
    font-weight: 800;
    margin-bottom: 0.5rem;
    letter-spacing: -1px;
    line-height: 1.1;
    background: linear-gradient(135deg, var(--color-accent) 0%, var(--color-teal) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero .tagline {
    font-size: 19px;
    color: var(--color-teal);
    margin-bottom: var(--spacing-md);
    font-weight: 600;
    letter-spacing: -0.3px;
}

.hero .subtitle {
    font-size: 16px;
    color: var(--color-text-secondary);
    max-width: 600px;
    margin: var(--spacing-lg) auto 0;
    line-height: 1.8;
}

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

.hero .subtitle-wonder {
    font-size: 15px;
    font-style: italic;
    color: var(--color-text-muted, rgba(255,255,255,0.5));
    max-width: 560px;
    margin: var(--spacing-md) auto var(--spacing-xl);
    line-height: 1.9;
    padding-top: var(--spacing-md);
    border-top: 1px solid rgba(255,255,255,0.08);
    letter-spacing: 0.01em;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    margin: var(--spacing-2xl) 0 var(--spacing-xl) 0;
    flex-wrap: wrap;
}

.social-links {
    display: flex;
    justify-content: center;
    gap: var(--spacing-xs);
    color: var(--color-text-muted);
    font-size: 13px;
}

.social-links a {
    color: var(--color-text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.2s ease;
}

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

/* ══════════════════════════════
   Buttons
══════════════════════════════ */
.btn {
    display: inline-block;
    padding: 12px 28px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    font-size: 14px;
    transition: all 0.25s ease;
    cursor: pointer;
    border: none;
    letter-spacing: -0.2px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-accent) 0%, var(--color-accent-hover) 100%);
    color: #0f1117;
    box-shadow: var(--shadow-md);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--glow-amber), var(--shadow-lg);
}

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

.btn-secondary:hover {
    background-color: var(--color-surface-raise);
    border-color: var(--color-teal);
    color: var(--color-teal);
}

.btn-outline {
    background-color: transparent;
    color: var(--color-teal);
    border: 1.5px solid var(--color-teal);
    font-weight: 600;
}

.btn-outline:hover {
    background-color: var(--color-teal-light);
    transform: translateY(-2px);
    box-shadow: var(--glow-teal);
}

.btn-small {
    padding: 10px 16px;
    font-size: 13px;
}

/* ══════════════════════════════
   Topics Section
══════════════════════════════ */
.topics {
    padding: var(--spacing-3xl) 0;
    background-color: var(--color-surface);
}

.topics h2,
.featured h2,
.notes h2,
.projects-teaser h2,
.cta h2 {
    font-size: 32px;
    font-weight: 800;
    margin-bottom: var(--spacing-xl);
    text-align: center;
    letter-spacing: -0.5px;
    color: var(--color-text);
}

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.topic-card {
    background-color: var(--color-bg);
    padding: var(--spacing-lg);
    border-radius: 12px;
    border: 1px solid var(--color-border);
    transition: all 0.3s ease;
    box-shadow: var(--shadow-sm);
}

.topic-card:hover {
    transform: translateY(-4px);
    border-color: var(--color-accent);
    box-shadow: var(--glow-amber), var(--shadow-lg);
}

.topic-card h3 {
    font-size: 16px;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    color: var(--color-accent);
    letter-spacing: -0.3px;
}

.topic-card p {
    font-size: 14px;
    color: var(--color-text-secondary);
    line-height: 1.7;
}

/* ══════════════════════════════
   Featured Articles
══════════════════════════════ */
.featured {
    padding: var(--spacing-3xl) 0;
    background-color: var(--color-bg);
}

.articles-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.article-card {
    border-bottom: 1px solid var(--color-border);
    padding-bottom: var(--spacing-xl);
    transition: all 0.3s ease;
}

.article-card:last-child {
    border-bottom: none;
    padding-bottom: 0;
}

.article-card:hover {
    transform: translateX(4px);
}

/* Article card with thumbnail image */
.article-card-with-image {
    display: flex;
    gap: var(--spacing-lg);
    align-items: flex-start;
    transform: none !important;
}

.article-card-with-image:hover .article-card-thumb img {
    transform: scale(1.04);
}

.article-card-thumb {
    flex-shrink: 0;
    width: 200px;
    height: 130px;
    border-radius: 10px;
    overflow: hidden;
    border: 1px solid var(--color-border);
    display: block;
}

.article-card-thumb img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    object-position: center 30%;
    transition: transform 0.4s ease;
    display: block;
}

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

@media (max-width: 600px) {
    .article-card-with-image {
        flex-direction: column;
        gap: var(--spacing-md);
    }

    .article-card-thumb {
        width: 100%;
        height: 180px;
    }
}

.article-card h3 {
    font-size: 19px;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    letter-spacing: -0.3px;
}

.article-card h3 a {
    color: var(--color-text);
    text-decoration: none;
    transition: color 0.2s ease;
}

.article-card h3 a:hover {
    color: var(--color-accent);
}

.article-meta {
    font-size: 12px;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-md);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-family: var(--font-mono);
}

.article-card p {
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.8;
}

.read-more {
    color: var(--color-teal);
    text-decoration: none;
    font-size: 14px;
    font-weight: 600;
    transition: all 0.2s ease;
    display: inline-flex;
    align-items: center;
}

.read-more:hover {
    color: var(--color-teal-hover);
    transform: translateX(4px);
}

.view-all {
    text-align: center;
    margin-top: var(--spacing-xl);
}

/* ══════════════════════════════
   Engineering Notes
══════════════════════════════ */
.notes {
    padding: var(--spacing-3xl) 0;
    background-color: var(--color-surface);
}

.notes-intro {
    font-size: 16px;
    color: var(--color-text-secondary);
    text-align: center;
    max-width: 600px;
    margin: 0 auto var(--spacing-xl);
    line-height: 1.8;
}

.notes-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: var(--spacing-lg);
}

.note-card {
    background-color: var(--color-bg);
    padding: var(--spacing-lg);
    border-radius: 12px;
    border: 1px solid var(--color-border);
    transition: all 0.3s ease;
}

.note-card:hover {
    transform: translateY(-4px);
    border-color: var(--color-teal);
    box-shadow: var(--glow-teal), var(--shadow-md);
}

.note-card h4 {
    font-size: 14px;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
    line-height: 1.6;
    letter-spacing: -0.2px;
}

.note-tag {
    display: inline-block;
    font-size: 11px;
    color: var(--color-teal);
    background-color: var(--color-teal-light);
    padding: 4px 10px;
    border-radius: 6px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.3px;
    font-family: var(--font-mono);
}

/* ══════════════════════════════
   Projects
══════════════════════════════ */
.projects-teaser {
    padding: var(--spacing-3xl) 0;
    background-color: var(--color-bg);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.project-card {
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: var(--spacing-lg);
    transition: all 0.3s ease;
}

.project-card:hover {
    transform: translateY(-4px);
    border-color: var(--color-accent);
    box-shadow: var(--glow-amber), var(--shadow-lg);
}

.project-card h3 {
    font-size: 16px;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
    letter-spacing: -0.2px;
    font-family: var(--font-mono);
}

.project-card p {
    font-size: 14px;
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.7;
}

/* ══════════════════════════════
   Newsletter CTA
══════════════════════════════ */
.cta {
    padding: var(--spacing-3xl) 0;
    text-align: center;
    background-color: var(--color-surface);
    border-top: 1px solid var(--color-border);
    border-bottom: 1px solid var(--color-border);
}

.cta p {
    font-size: 16px;
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-xl);
    line-height: 1.8;
}

.newsletter-form {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
    flex-wrap: wrap;
}

.newsletter-form input {
    padding: 12px 16px;
    border: 1.5px solid var(--color-border);
    border-radius: 8px;
    font-family: var(--font-family);
    font-size: 14px;
    width: 220px;
    transition: all 0.2s ease;
    background-color: var(--color-surface-alt);
    color: var(--color-text);
}

.newsletter-form input::placeholder {
    color: var(--color-text-muted);
}

.newsletter-form input:focus {
    outline: none;
    border-color: var(--color-teal);
    box-shadow: 0 0 0 3px var(--color-teal-light);
    background-color: var(--color-surface-raise);
}

.newsletter-form button {
    width: auto;
}

/* ══════════════════════════════
   Footer
══════════════════════════════ */
.footer {
    border-top: 1px solid var(--color-border);
    padding: var(--spacing-xl) 0;
    background-color: var(--color-surface);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-lg);
}

.footer p {
    font-size: 13px;
    color: var(--color-text-muted);
    font-weight: 500;
}

.footer-links {
    display: flex;
    gap: var(--spacing-xs);
    font-size: 13px;
}

.footer-links a {
    color: var(--color-text-muted);
    text-decoration: none;
    transition: color 0.2s ease;
    font-weight: 500;
}

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

/* ══════════════════════════════
   Responsive — Tablet ≤768px
══════════════════════════════ */
@media (max-width: 768px) {
    body {
        font-size: 15px;
    }

    .hero {
        padding: var(--spacing-2xl) var(--spacing-md) var(--spacing-xl);
    }

    .hero h1 {
        font-size: 40px;
    }

    .hero .tagline {
        font-size: 16px;
    }

    .hero .subtitle {
        font-size: 15px;
    }

    .hero-buttons {
        flex-direction: column;
        align-items: center;
        margin: var(--spacing-xl) 0 var(--spacing-lg) 0;
    }

    .hero-buttons .btn {
        width: 100%;
        max-width: 280px;
        text-align: center;
    }

    .topics h2,
    .featured h2,
    .notes h2,
    .projects-teaser h2,
    .cta h2 {
        font-size: 26px;
    }

    .newsletter-form {
        flex-direction: column;
        align-items: center;
    }

    .newsletter-form input {
        width: 100%;
        max-width: 320px;
    }

    .newsletter-form .btn {
        width: 100%;
        max-width: 320px;
        text-align: center;
    }

    .footer-content {
        flex-direction: column;
        text-align: center;
    }

    .page-header h1 {
        font-size: 28px !important;
    }

    .article-card:hover {
        transform: none;
    }
}

/* ══════════════════════════════
   Responsive — Mobile ≤480px
══════════════════════════════ */
@media (max-width: 480px) {
    /* Hamburger */
    .nav-toggle {
        display: flex;
        align-items: center;
        justify-content: center;
        min-width: 44px;
        min-height: 44px;
    }

    .nav-menu {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: rgba(15, 17, 23, 0.98);
        border-bottom: 1px solid var(--color-border);
        flex-direction: column;
        gap: 0;
        padding: var(--spacing-sm) 0;
        box-shadow: var(--shadow-md);
        z-index: 99;
    }

    .nav-menu.is-open {
        display: flex;
    }

    .nav-menu li {
        width: 100%;
    }

    .nav-menu a {
        display: flex;
        align-items: center;
        padding: 14px var(--spacing-md);
        font-size: 15px;
        border-bottom: 1px solid var(--color-border-light);
        min-height: 44px;
    }

    .nav-menu li:last-child a {
        border-bottom: none;
    }

    .hero {
        padding: var(--spacing-xl) var(--spacing-sm);
    }

    .hero h1 {
        font-size: 34px;
    }

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

    .btn {
        padding: 14px 24px;
        font-size: 14px;
        min-height: 44px;
        display: inline-flex;
        align-items: center;
        justify-content: center;
    }

    .read-more {
        padding: 8px 0;
        min-height: 44px;
    }

    .social-links {
        flex-wrap: wrap;
        gap: var(--spacing-sm);
        row-gap: var(--spacing-xs);
    }

    .social-links a {
        min-height: 44px;
        display: inline-flex;
        align-items: center;
    }

    .filter-buttons {
        gap: var(--spacing-xs);
    }

    .filter-btn {
        min-height: 44px;
        padding: 10px 16px;
    }

    .contact-grid {
        grid-template-columns: 1fr !important;
        gap: var(--spacing-lg) !important;
    }

    .pillars,
    .skills {
        grid-template-columns: 1fr !important;
    }
}

/* ══════════════════════════════
   Global transitions + selection
══════════════════════════════ */
a {
    transition: color 0.2s ease;
}

::selection {
    background-color: var(--color-accent-light);
    color: var(--color-accent);
}