/* ---- Variables (light) ---- */
:root {
    color-scheme: light dark;

    /* Color */
    --text-primary: #1d1d1f;
    --text-secondary: #6e6e73;
    --text-tertiary: #6e6e73;
    --bg-primary: #fff;
    --bg-secondary: #f5f5f7;
    --bg-elevated: #fff;
    --border-color: #d2d2d7;
    --border-light: #e8e8ed;
    --hairline: rgba(0, 0, 0, 0.08);
    --card-border-color: transparent;
    --accent: #0066cc;
    --accent-hover: #0071e3;
    --gradient-accent: linear-gradient(96deg, #0066e0 0%, #009cae 100%);
    --glow-accent: rgba(0, 113, 227, 0.22);

    /* Type (fluid) */
    --font-display: clamp(3rem, 2rem + 4.5vw, 5rem);
    --font-title-1: clamp(2rem, 1.5rem + 2.6vw, 3.5rem);
    --font-title-2: clamp(2rem, 1.7rem + 1.6vw, 3rem);
    --font-title-3: clamp(1.3125rem, 1.2rem + 0.5vw, 1.5rem);
    --font-body-lg: clamp(1.0625rem, 1rem + 0.5vw, 1.3125rem);
    --font-body: 1.0625rem;
    --font-callout: 0.9375rem;
    --font-footnote: 0.8125rem;
    --font-caption: 0.75rem;
    --tracking-display: -0.04em;
    --tracking-title: -0.025em;
    --tracking-body: -0.011em;

    /* Space */
    --space-xs: 8px;
    --space-sm: 12px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;
    --space-3xl: 64px;
    --space-4xl: 96px;
    --section-pad: clamp(88px, 6vw + 64px, 152px);

    /* Shape */
    --radius: 12px;
    --radius-lg: 20px;
    --radius-xl: 28px;

    /* Elevation */
    --shadow-card: 0 1px 2px rgba(0, 0, 0, 0.05), 0 4px 16px rgba(0, 0, 0, 0.06);
    --shadow-card-hover: 0 2px 6px rgba(0, 0, 0, 0.05), 0 12px 32px rgba(0, 0, 0, 0.10);
    --shadow-icon: 0 10px 24px rgba(0, 0, 0, 0.12), 0 28px 64px var(--glow-accent);

    /* Motion */
    --ease-out: cubic-bezier(0.22, 1, 0.36, 1);
    --ease-inout: cubic-bezier(0.65, 0, 0.35, 1);
    --ease-spring: cubic-bezier(0.32, 1.25, 0.32, 1);
    --ease-sheet: cubic-bezier(0.32, 0.72, 0, 1);
    --dur-fast: 150ms;
    --dur-base: 300ms;
    --dur-slow: 500ms;
    --dur-reveal: 800ms;
}

/* ---- Variables (dark) ---- */
@media (prefers-color-scheme: dark) {
    :root {
        --text-primary: #f5f5f7;
        --text-secondary: #a1a1a6;
        --text-tertiary: #86868b;
        --bg-primary: #000;
        --bg-secondary: #161617;
        --bg-elevated: #1c1c1e;
        --border-color: #38383a;
        --border-light: #2c2c2e;
        --hairline: rgba(255, 255, 255, 0.14);
        --card-border-color: rgba(255, 255, 255, 0.14);
        --accent: #2997ff;
        --accent-hover: #40a9ff;
        --gradient-accent: linear-gradient(96deg, #2997ff 0%, #64d2ff 100%);
        --glow-accent: rgba(41, 151, 255, 0.28);
        --shadow-card: 0 1px 2px rgba(0, 0, 0, 0.45), 0 4px 16px rgba(0, 0, 0, 0.55);
        --shadow-card-hover: 0 2px 6px rgba(0, 0, 0, 0.45), 0 12px 32px rgba(0, 0, 0, 0.65);
    }
}

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: 64px;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text", "Helvetica Neue", Helvetica, Arial, sans-serif;
    font-size: var(--font-body);
    letter-spacing: var(--tracking-body);
    color: var(--text-primary);
    background: var(--bg-primary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}

h1, h2, h3, h4 {
    text-wrap: balance;
}

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

/* ---- Gradient headline accent ---- */
.gradient-text {
    color: var(--accent);
}

@supports ((-webkit-background-clip: text) or (background-clip: text)) {
    .gradient-text {
        background: var(--gradient-accent);
        -webkit-background-clip: text;
        background-clip: text;
        -webkit-text-fill-color: transparent;
        color: transparent;
    }
}

/* ---- Nav (sticky frosted glass; transparent while at top of page) ---- */
.nav-sentinel {
    position: absolute;
    top: 0;
    height: 1px;
    width: 1px;
}

nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.72);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 0.5px solid rgba(0, 0, 0, 0.1);
    transition: background 400ms var(--ease-inout), border-color 400ms var(--ease-inout);
}

nav.at-top {
    background: transparent;
    border-bottom-color: transparent;
}

@supports not (backdrop-filter: blur(1px)) {
    nav {
        background: rgba(255, 255, 255, 0.95);
    }
}

@media (prefers-color-scheme: dark) {
    nav {
        background: rgba(0, 0, 0, 0.72);
        border-bottom-color: rgba(255, 255, 255, 0.1);
    }
    nav.at-top {
        background: transparent;
        border-bottom-color: transparent;
    }
    @supports not (backdrop-filter: blur(1px)) {
        nav {
            background: rgba(0, 0, 0, 0.95);
        }
    }
}

nav .nav-inner {
    max-width: 980px;
    margin: 0 auto;
    padding: 0 22px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

nav .nav-title {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-primary);
    text-decoration: none;
    letter-spacing: -0.01em;
    transition: opacity var(--dur-base) var(--ease-inout);
}

nav .nav-title:hover {
    opacity: 0.7;
}

nav .nav-links {
    display: flex;
    gap: 28px;
    list-style: none;
}

nav .nav-links a {
    font-size: 12px;
    color: var(--text-primary);
    opacity: 0.8;
    text-decoration: none;
    transition: opacity 200ms var(--ease-inout);
}

nav .nav-links a:hover {
    opacity: 1;
}

/* ---- Fade-in reveal (one-shot, via IntersectionObserver) ---- */
.fade-in {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity var(--dur-reveal) var(--ease-out), transform var(--dur-reveal) var(--ease-out);
}

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

/* ---- Staggered reveal for grouped children ---- */
.stagger > .fade-in:nth-child(1) { transition-delay: 0s; }
.stagger > .fade-in:nth-child(2) { transition-delay: 80ms; }
.stagger > .fade-in:nth-child(3) { transition-delay: 160ms; }
.stagger > .fade-in:nth-child(4) { transition-delay: 240ms; }
.stagger > .fade-in:nth-child(5) { transition-delay: 320ms; }
.stagger > .fade-in:nth-child(6) { transition-delay: 400ms; }
.stagger > .fade-in:nth-child(n+7) { transition-delay: 480ms; }

/* ---- Footer (shared, all pages) ---- */
footer {
    padding: var(--space-xl) 22px;
    border-top: 0.5px solid var(--hairline);
    background: var(--bg-secondary);
}

footer .footer-inner {
    max-width: 980px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--space-sm);
}

footer .copyright {
    font-size: var(--font-caption);
    color: var(--text-secondary);
}

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

footer .footer-links a {
    font-size: var(--font-caption);
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 200ms var(--ease-inout);
}

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

/* ---- Responsive: hide nav links on mobile (footer carries the links) ---- */
@media (max-width: 734px) {
    .nav-links {
        display: none !important;
    }
}

/* ---- Reduced motion (Apple HIG): show everything, skip animation ---- */
@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }
    .fade-in,
    .stagger > .fade-in {
        opacity: 1;
        transform: none;
        transition: none;
    }
    .hero > * {
        opacity: 1;
        transform: none;
        animation: none;
    }
    nav {
        transition: none;
    }
}