/* 1 Level Up — shared design system
   Language: Vercel × Resend × x.ai — monochrome, geometric, full-bleed */

:root {
    --bg: #FAFAFA;
    --bg-elevated: #FFFFFF;
    --bg-muted: #F5F5F5;
    --bg-inverse: #050505;
    --bg-inverse-soft: #0A0A0A;
    --fg: #0A0A0A;
    --fg-soft: #171717;
    --fg-muted: #737373;
    --fg-subtle: #A3A3A3;
    --fg-inverse: #FAFAFA;
    --fg-inverse-muted: #A1A1A1;
    --border: #EAEAEA;
    --border-strong: #D4D4D4;
    --border-inverse: rgba(255, 255, 255, 0.12);
    --accent: #0A0A0A;
    --work: #22C55E;
    --health: #38BDF8;
    --rel: #A78BFA;
    --disc: #FB7185;
    --radius: 8px;
    --radius-sm: 6px;
    --shadow: 0 0 0 1px rgba(0, 0, 0, 0.03), 0 2px 8px rgba(0, 0, 0, 0.04);
    --wrap: min(1120px, calc(100% - 2.5rem));
    --font: 'Geist', 'Geist Sans', ui-sans-serif, system-ui, sans-serif;
    --font-mono: 'Geist Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    /* Soft syntax tokens — multi-colour on graphite, not neon */
    --syn-comment: #8A8A8A;
    --syn-punct: #9CA3AF;
    --syn-key: #3B6EA8;
    --syn-str: #2F7A52;
    --syn-num: #9A6B2F;
    --syn-kw: #6B5B95;
    --syn-comment-inv: #6E6E6E;
    --syn-punct-inv: #5A5A5A;
    --syn-key-inv: #8BA4C7;
    --syn-str-inv: #8FBF9E;
    --syn-num-inv: #C4A67A;
    --syn-kw-inv: #A898C4;
    --ease: cubic-bezier(0.16, 1, 0.3, 1);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--fg);
    line-height: 1.55;
    font-size: 1rem;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
}

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

a {
    color: inherit;
}

:focus-visible {
    outline: 2px solid var(--fg);
    outline-offset: 3px;
}

.skip-link {
    position: absolute;
    left: 1rem;
    top: -4rem;
    background: var(--fg);
    color: var(--fg-inverse);
    padding: 0.6rem 1rem;
    z-index: 10000;
    border-radius: var(--radius-sm);
    text-decoration: none;
    font-size: 0.9rem;
    font-weight: 500;
}

.skip-link:focus {
    top: 1rem;
}

.wrap {
    width: var(--wrap);
    margin: 0 auto;
}

/* ===== NAV ===== */
.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(250, 250, 250, 0.72);
    backdrop-filter: blur(16px) saturate(1.4);
    -webkit-backdrop-filter: blur(16px) saturate(1.4);
    border-bottom: 1px solid transparent;
    transition: border-color 0.25s var(--ease), background 0.25s var(--ease);
}

.site-header.scrolled {
    border-bottom-color: var(--border);
    background: rgba(250, 250, 250, 0.88);
}

.site-header.on-dark {
    background: rgba(5, 5, 5, 0.72);
    border-bottom-color: transparent;
}

.site-header.on-dark.scrolled {
    border-bottom-color: var(--border-inverse);
    background: rgba(5, 5, 5, 0.88);
}

.site-header.on-dark .logo,
.site-header.on-dark .nav-links a {
    color: var(--fg-inverse);
}

.site-header.on-dark .nav-links a {
    color: var(--fg-inverse-muted);
}

.site-header.on-dark .nav-links a:hover {
    color: var(--fg-inverse);
}

.site-header.on-dark .menu-btn {
    border-color: var(--border-inverse);
    background: transparent;
}

.site-header.on-dark .menu-btn span {
    background: var(--fg-inverse);
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    min-height: 64px;
    gap: 1rem;
}

.logo {
    display: inline-flex;
    align-items: baseline;
    gap: 0.3rem;
    text-decoration: none;
    font-weight: 600;
    font-size: 1.05rem;
    letter-spacing: -0.04em;
    color: var(--fg);
}

.logo b {
    font-weight: 700;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    list-style: none;
}

.nav-links a {
    text-decoration: none;
    color: var(--fg-muted);
    font-size: 0.875rem;
    font-weight: 500;
    letter-spacing: -0.01em;
    transition: color 0.15s ease;
}

.nav-links a:hover {
    color: var(--fg);
}

.nav-links a.btn {
    color: var(--fg-inverse);
}

.nav-links a.btn:hover {
    color: var(--fg-inverse);
}

.btn.nav-book {
    display: none;
}

.nav-login {
    color: var(--fg-subtle) !important;
    font-size: 0.8125rem !important;
}

.menu-btn {
    display: none;
    width: 40px;
    height: 40px;
    border: 1px solid var(--border);
    background: var(--bg-elevated);
    border-radius: var(--radius-sm);
    cursor: pointer;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 5px;
}

.menu-btn span {
    display: block;
    width: 14px;
    height: 1.5px;
    background: var(--fg);
}

/* ===== BUTTONS ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.4rem;
    padding: 0.7rem 1.1rem;
    background: var(--fg);
    color: var(--fg-inverse);
    text-decoration: none;
    border: 1px solid var(--fg);
    border-radius: var(--radius);
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 500;
    letter-spacing: -0.01em;
    cursor: pointer;
    transition: background 0.15s ease, color 0.15s ease, border-color 0.15s ease, transform 0.2s var(--ease);
}

.btn:hover {
    background: #262626;
    transform: translateY(-1px);
}

.btn:disabled {
    opacity: 0.55;
    cursor: not-allowed;
    transform: none;
}

.btn-ghost {
    background: transparent;
    color: var(--fg);
    border-color: var(--border-strong);
}

.btn-ghost:hover {
    background: var(--bg-muted);
    border-color: var(--fg);
    color: var(--fg);
}

.btn-light {
    background: var(--fg-inverse);
    color: var(--fg);
    border-color: var(--fg-inverse);
}

.btn-light:hover {
    background: #fff;
}

.btn-on-dark.btn-ghost {
    color: var(--fg-inverse);
    border-color: var(--border-inverse);
}

.btn-on-dark.btn-ghost:hover {
    background: rgba(255, 255, 255, 0.06);
    border-color: rgba(255, 255, 255, 0.35);
    color: var(--fg-inverse);
}

/* ===== TYPE ===== */
.kicker {
    color: var(--fg-muted);
    font-weight: 500;
    font-size: 0.8125rem;
    letter-spacing: -0.01em;
    margin-bottom: 1rem;
}

.kicker-inverse {
    color: var(--fg-inverse-muted);
}

/* ===== SYNTAX / CODE STATUS ===== */
.code-line,
.code-status {
    font-family: var(--font-mono);
    font-weight: 450;
    letter-spacing: -0.02em;
    font-variant-ligatures: none;
}

.code-status {
    display: inline-flex;
    align-items: baseline;
    flex-wrap: wrap;
    gap: 0.35rem;
    font-size: 0.75rem;
    line-height: 1.4;
}

.kicker.code-status {
    display: flex;
    margin-bottom: 1rem;
    color: var(--fg-muted);
}

.tag.code-status {
    margin-bottom: 0.85rem;
    color: var(--fg-muted);
}

.offer.featured .tag.code-status {
    color: var(--fg-inverse-muted);
}

.tok-comment { color: var(--syn-comment); }
.tok-punct { color: var(--syn-punct); }
.tok-key { color: var(--syn-key); }
.tok-str { color: var(--syn-str); }
.tok-num { color: var(--syn-num); }
.tok-kw { color: var(--syn-kw); }

.section-inverse .tok-comment,
.on-dark .tok-comment,
.hero .tok-comment { color: var(--syn-comment-inv); }

.section-inverse .tok-punct,
.on-dark .tok-punct,
.hero .tok-punct { color: var(--syn-punct-inv); }

.section-inverse .tok-key,
.on-dark .tok-key,
.hero .tok-key { color: var(--syn-key-inv); }

.section-inverse .tok-str,
.on-dark .tok-str,
.hero .tok-str { color: var(--syn-str-inv); }

.section-inverse .tok-num,
.on-dark .tok-num,
.hero .tok-num { color: var(--syn-num-inv); }

.section-inverse .tok-kw,
.on-dark .tok-kw,
.hero .tok-kw { color: var(--syn-kw-inv); }

.offer.featured .tok-comment { color: var(--syn-comment-inv); }
.offer.featured .tok-punct { color: var(--syn-punct-inv); }
.offer.featured .tok-key { color: var(--syn-key-inv); }
.offer.featured .tok-str { color: var(--syn-str-inv); }
.offer.featured .tok-num { color: var(--syn-num-inv); }
.offer.featured .tok-kw { color: var(--syn-kw-inv); }

.tok-work { color: var(--work) !important; }
.tok-health { color: var(--health) !important; }
.tok-rel { color: var(--rel) !important; }
.tok-disc { color: var(--disc) !important; }

h1,
.h1 {
    font-weight: 600;
    font-size: clamp(2.75rem, 7vw, 4.75rem);
    line-height: 1.02;
    letter-spacing: -0.055em;
    margin-bottom: 1.15rem;
}

h2,
.h2 {
    font-weight: 600;
    font-size: clamp(1.85rem, 4vw, 2.75rem);
    letter-spacing: -0.045em;
    line-height: 1.08;
    margin-bottom: 0.75rem;
}

h3,
.h3 {
    font-weight: 600;
    letter-spacing: -0.03em;
}

.lede {
    font-size: 1.125rem;
    color: var(--fg-muted);
    max-width: 34rem;
    margin-bottom: 1.75rem;
    letter-spacing: -0.015em;
    line-height: 1.55;
}

.section-intro {
    color: var(--fg-muted);
    max-width: 34rem;
    margin-bottom: 2.25rem;
    letter-spacing: -0.01em;
}

.fine {
    color: var(--fg-subtle);
    font-size: 0.8125rem;
    letter-spacing: -0.01em;
}

.cta-row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.65rem;
    margin-bottom: 1rem;
}

/* ===== SECTIONS ===== */
section {
    padding: 5.5rem 0;
}

.section-inverse {
    background: var(--bg-inverse);
    color: var(--fg-inverse);
}

.section-inverse .kicker {
    color: var(--fg-inverse-muted);
}

.section-inverse .section-intro,
.section-inverse p {
    color: var(--fg-inverse-muted);
}

.section-inverse h2 {
    color: var(--fg-inverse);
}

/* ===== FOOTER ===== */
.site-footer {
    border-top: 1px solid var(--border);
    padding: 1.5rem 0 2rem;
    background: var(--bg);
}

.footer-row {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    flex-wrap: wrap;
    color: var(--fg-muted);
    font-size: 0.8125rem;
}

.footer-row nav {
    display: flex;
    gap: 1.15rem;
}

.footer-row a {
    color: var(--fg-muted);
    text-decoration: none;
    transition: color 0.15s ease;
}

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

/* ===== MOTION ===== */
@keyframes fade-up {
    from {
        opacity: 0;
        transform: translateY(18px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes bar-grow {
    from {
        transform: scaleX(0);
    }
    to {
        transform: scaleX(1);
    }
}

@keyframes pulse-line {
    0%,
    100% {
        opacity: 0.35;
    }
    50% {
        opacity: 0.7;
    }
}

.reveal {
    opacity: 0;
    animation: fade-up 0.9s var(--ease) forwards;
}

.reveal-d1 {
    animation-delay: 0.08s;
}

.reveal-d2 {
    animation-delay: 0.18s;
}

.reveal-d3 {
    animation-delay: 0.28s;
}

.reveal-d4 {
    animation-delay: 0.4s;
}

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    .reveal,
    .reveal-d1,
    .reveal-d2,
    .reveal-d3,
    .reveal-d4 {
        opacity: 1;
        animation: none;
    }

    .btn {
        transition: none;
    }
}

/* ===== MOBILE NAV ===== */
@media (max-width: 900px) {
    .menu-btn {
        display: flex;
    }

    .btn.nav-book {
        display: inline-flex;
        margin-left: auto;
        margin-right: 0.5rem;
        padding: 0.5rem 0.85rem;
        font-size: 0.8125rem;
    }

    .nav-links a.btn {
        display: none;
    }

    .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        flex-direction: column;
        align-items: stretch;
        gap: 0;
        background: var(--bg);
        border-bottom: 1px solid var(--border);
        padding: 0.4rem 1.25rem 1rem;
    }

    .site-header.on-dark .nav-links {
        background: var(--bg-inverse);
        border-bottom-color: var(--border-inverse);
    }

    .nav-links.open {
        display: flex;
        z-index: 200;
    }

    .nav-links a {
        padding: 0.85rem 0;
        border-top: 1px solid var(--border);
    }

    .site-header.on-dark .nav-links a {
        border-top-color: var(--border-inverse);
    }

    .nav {
        position: relative;
    }

    .menu-btn {
        z-index: 201;
    }

    section {
        padding: 3.75rem 0;
    }
}