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

/* ===== Custom Properties ===== */
:root {
    /* Colors — dark technical palette */
    --color-bg: #0a0a0f;
    --color-bg-elevated: #12121a;
    --color-bg-card: #1a1a25;
    --color-bg-card-hover: #22222f;
    --color-border: #2a2a3a;
    --color-border-hover: #3a3a50;
    --color-text-primary: #e8e8ed;
    --color-text-secondary: #9a9ab0;
    --color-text-muted: #6a6a80;
    --color-accent: #6c8cff;
    --color-accent-hover: #8ba4ff;
    --color-accent-subtle: rgba(108, 140, 255, 0.1);
    --color-tag-bg: rgba(108, 140, 255, 0.08);
    --color-tag-border: rgba(108, 140, 255, 0.2);

    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;

    --text-xs: 0.75rem;
    --text-sm: 0.875rem;
    --text-base: 1rem;
    --text-lg: 1.125rem;
    --text-xl: 1.25rem;
    --text-2xl: 1.5rem;
    --text-3xl: 2rem;
    --text-4xl: 2.75rem;
    --text-5xl: 3.5rem;

    --weight-normal: 400;
    --weight-medium: 500;
    --weight-semibold: 600;
    --weight-bold: 700;

    --leading-tight: 1.2;
    --leading-normal: 1.6;

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;
    --space-4xl: 6rem;

    /* Layout */
    --max-width: 1140px;
    --nav-height: 64px;

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

/* ===== Base ===== */
html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--nav-height);
}

body {
    font-family: var(--font-sans);
    font-size: var(--text-base);
    font-weight: var(--weight-normal);
    line-height: var(--leading-normal);
    color: var(--color-text-primary);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

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

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

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

.section {
    padding: var(--space-4xl) 0;
}

.section-heading {
    font-size: var(--text-3xl);
    font-weight: var(--weight-bold);
    line-height: var(--leading-tight);
    margin-bottom: var(--space-2xl);
    color: var(--color-text-primary);
}

/* ===== Navigation ===== */
#navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height);
    background: rgba(10, 10, 15, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
    z-index: 1000;
}

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

.nav-logo {
    font-size: var(--text-xl);
    font-weight: var(--weight-bold);
    color: var(--color-text-primary);
    letter-spacing: 0.02em;
}

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

.nav-links {
    display: flex;
    list-style: none;
    gap: var(--space-xl);
}

.nav-link {
    font-size: var(--text-sm);
    font-weight: var(--weight-medium);
    color: var(--color-text-secondary);
    letter-spacing: 0.02em;
    text-transform: uppercase;
    transition: color var(--transition-fast);
}

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

.external-icon {
    font-size: var(--text-xs);
}

/* Mobile nav toggle */
.nav-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
}

.nav-toggle-bar {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--color-text-secondary);
    border-radius: 1px;
    transition: transform var(--transition-base), opacity var(--transition-base);
}

.nav-toggle.active .nav-toggle-bar:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}

.nav-toggle.active .nav-toggle-bar:nth-child(2) {
    opacity: 0;
}

.nav-toggle.active .nav-toggle-bar:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* ===== Hero ===== */
#hero {
    padding-top: calc(var(--nav-height) + var(--space-3xl));
    padding-bottom: var(--space-xl);
    display: flex;
    align-items: center;
}

.section-tight {
    padding-top: var(--space-2xl);
}

.hero-content {
    max-width: 720px;
}

.hero-title {
    font-size: var(--text-5xl);
    font-weight: var(--weight-bold);
    line-height: var(--leading-tight);
    margin-bottom: var(--space-md);
}

.hero-subtitle {
    font-size: var(--text-xl);
    font-weight: var(--weight-medium);
    color: var(--color-accent);
    margin-bottom: var(--space-lg);
    letter-spacing: 0.01em;
}

.hero-body {
    font-size: var(--text-lg);
    color: var(--color-text-secondary);
    line-height: var(--leading-normal);
    margin-bottom: var(--space-2xl);
    max-width: 600px;
}

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

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: 0.75rem 1.5rem;
    font-size: var(--text-sm);
    font-weight: var(--weight-semibold);
    border-radius: 6px;
    transition: all var(--transition-base);
    cursor: pointer;
    border: none;
    text-decoration: none;
}

.btn-primary {
    background: var(--color-accent);
    color: #fff;
}

.btn-primary:hover {
    background: var(--color-accent-hover);
    color: #fff;
    transform: translateY(-1px);
}

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

.btn-secondary:hover {
    color: var(--color-text-primary);
    border-color: var(--color-border-hover);
    transform: translateY(-1px);
}

.btn-card {
    background: var(--color-accent-subtle);
    color: var(--color-accent);
    font-size: var(--text-sm);
    padding: 0.5rem 1rem;
}

.btn-card:hover {
    background: var(--color-accent);
    color: #fff;
}

.btn-card-alt {
    background: transparent;
    color: var(--color-text-muted);
    font-size: var(--text-sm);
    padding: 0.5rem 1rem;
    border: 1px solid var(--color-border);
}

.btn-card-alt:hover {
    color: var(--color-text-secondary);
    border-color: var(--color-border-hover);
}

/* ===== Projects Grid ===== */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    gap: var(--space-xl);
}

/* ===== Project Card ===== */
.card {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: 10px;
    padding: var(--space-xl);
    display: flex;
    flex-direction: column;
    transition: transform var(--transition-base), border-color var(--transition-base), box-shadow var(--transition-base);
}

.card:hover {
    transform: translateY(-4px);
    border-color: var(--color-border-hover);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
}

.card-content {
    flex: 1;
    margin-bottom: var(--space-lg);
}

.card-title {
    font-size: var(--text-xl);
    font-weight: var(--weight-bold);
    margin-bottom: var(--space-sm);
    color: var(--color-text-primary);
}

.card-value {
    font-size: var(--text-sm);
    font-weight: var(--weight-medium);
    color: var(--color-accent);
    margin-bottom: var(--space-sm);
}

.card-why {
    font-size: var(--text-sm);
    color: var(--color-text-muted);
    font-style: italic;
    margin-bottom: var(--space-md);
    padding-left: var(--space-md);
    border-left: 2px solid var(--color-border);
}

.card-description {
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
    line-height: var(--leading-normal);
}

/* Card tags */
.card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
    margin-top: var(--space-md);
}

.tag {
    display: inline-block;
    font-size: var(--text-xs);
    font-weight: var(--weight-medium);
    color: var(--color-accent);
    background: var(--color-tag-bg);
    border: 1px solid var(--color-tag-border);
    padding: 0.2rem 0.6rem;
    border-radius: 100px;
    letter-spacing: 0.01em;
}

/* Card freshness */
.card-freshness {
    font-size: var(--text-xs);
    color: var(--color-text-muted);
    margin-top: var(--space-md);
}

/* Card footer (links + expand button) */
.card-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-sm);
    flex-wrap: wrap;
}

.card-links {
    display: flex;
    gap: var(--space-sm);
    flex-wrap: wrap;
}

/* Card expand button */
.card-expand-btn {
    font-family: var(--font-sans);
    font-size: var(--text-xs);
    font-weight: var(--weight-medium);
    color: var(--color-text-muted);
    background: none;
    border: 1px solid var(--color-border);
    border-radius: 4px;
    padding: 0.35rem 0.75rem;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.card-expand-btn:hover {
    color: var(--color-text-secondary);
    border-color: var(--color-border-hover);
}

.card-expand-btn[aria-expanded="true"] {
    color: var(--color-accent);
    border-color: var(--color-tag-border);
}

/* Card expandable detail */
.card-expand-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 350ms ease, margin 350ms ease, opacity 250ms ease;
    opacity: 0;
    margin-top: 0;
}

.card.expanded .card-expand-content {
    max-height: 600px;
    opacity: 1;
    margin-top: var(--space-lg);
    margin-bottom: var(--space-lg);
}

.card-detail {
    padding: var(--space-md);
    background: var(--color-bg-elevated);
    border-radius: 6px;
    margin-bottom: var(--space-sm);
}

.card-detail:last-child {
    margin-bottom: 0;
}

.card-detail h4 {
    font-size: var(--text-xs);
    font-weight: var(--weight-semibold);
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--space-xs);
}

.card-detail p {
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
    line-height: var(--leading-normal);
}

/* ===== What's Next ===== */
.whats-next {
    margin-top: var(--space-2xl);
    padding: var(--space-lg);
    border: 1px dashed var(--color-border);
    border-radius: 8px;
    text-align: center;
}

.whats-next p {
    font-size: var(--text-sm);
    color: var(--color-text-muted);
    font-style: italic;
}

/* ===== How I Build ===== */
.build-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: var(--space-xl);
}

.build-item {
    padding: var(--space-lg);
    border-left: 3px solid var(--color-accent);
    background: var(--color-bg-elevated);
    border-radius: 0 8px 8px 0;
}

.build-title {
    font-size: var(--text-base);
    font-weight: var(--weight-semibold);
    color: var(--color-text-primary);
    margin-bottom: var(--space-sm);
}

.build-description {
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
    line-height: var(--leading-normal);
}

/* ===== Positioning (What Ties These Together) ===== */
.positioning-content {
    max-width: 720px;
}

.positioning-content p {
    font-size: var(--text-lg);
    color: var(--color-text-secondary);
    line-height: var(--leading-normal);
    margin-bottom: var(--space-lg);
}

.positioning-content p:first-child {
    font-size: var(--text-xl);
    color: var(--color-text-primary);
    font-weight: var(--weight-medium);
}

.positioning-content p:last-child {
    margin-bottom: 0;
}

/* ===== About ===== */
.about-content p {
    font-size: var(--text-lg);
    color: var(--color-text-secondary);
    line-height: var(--leading-normal);
    max-width: 720px;
    margin-bottom: var(--space-md);
}

.about-content p:last-of-type {
    color: var(--color-text-primary);
    font-weight: var(--weight-medium);
}

.about-links {
    display: flex;
    gap: var(--space-md);
    margin-top: var(--space-xl);
    flex-wrap: wrap;
}

/* ===== Footer ===== */
#footer {
    border-top: 1px solid var(--color-border);
    padding: var(--space-2xl) 0;
}

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

.footer-note {
    font-size: var(--text-sm);
    color: var(--color-text-muted);
    max-width: 480px;
}

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

.footer-links a {
    font-size: var(--text-sm);
    font-weight: var(--weight-medium);
    color: var(--color-text-secondary);
}

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

.footer-sep {
    color: var(--color-text-muted);
    font-size: var(--text-xs);
}

.footer-copy {
    font-size: var(--text-xs);
    color: var(--color-text-muted);
}

/* ===== Responsive — Tablet (481px+) ===== */
@media (min-width: 481px) {
    .projects-grid {
        grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    }
}

/* ===== Responsive — Desktop (769px+) ===== */
@media (min-width: 769px) {
    .section-heading {
        font-size: var(--text-4xl);
    }

    .hero-title {
        font-size: var(--text-5xl);
    }
}

/* ===== Responsive — Mobile (≤768px) ===== */
@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }

    .nav-links {
        display: none;
        position: absolute;
        top: var(--nav-height);
        left: 0;
        right: 0;
        flex-direction: column;
        background: rgba(10, 10, 15, 0.95);
        backdrop-filter: blur(12px);
        -webkit-backdrop-filter: blur(12px);
        border-bottom: 1px solid var(--color-border);
        padding: var(--space-lg) var(--space-xl);
        gap: var(--space-lg);
    }

    .nav-links.open {
        display: flex;
    }

    .hero-title {
        font-size: var(--text-4xl);
    }

    .hero-subtitle {
        font-size: var(--text-lg);
    }

    #hero {
        padding-top: calc(var(--nav-height) + var(--space-2xl));
        padding-bottom: var(--space-md);
    }

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

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

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

    .section-heading {
        font-size: var(--text-2xl);
    }

    .card-footer {
        flex-direction: column;
        align-items: flex-start;
    }
}

/* ===== Responsive — Small Mobile (≤480px) ===== */
@media (max-width: 480px) {
    .container {
        padding: 0 var(--space-md);
    }

    .hero-title {
        font-size: var(--text-3xl);
    }

    .hero-ctas {
        flex-direction: column;
    }

    .hero-ctas .btn {
        text-align: center;
        justify-content: center;
    }

    .about-links {
        flex-direction: column;
    }

    .about-links .btn {
        text-align: center;
        justify-content: center;
    }
}