/* ============================================================
   Synap — design system
   Dark "neural signal" technical brand.
   Display: Bricolage Grotesque · Body: Hanken Grotesk · Mono: JetBrains Mono
   ============================================================ */

:root {
    /* Surface */
    --bg: #0a0b10;
    --bg-grad-top: #0d0f18;
    --surface: #111320;
    --surface-2: #161929;
    --surface-3: #1c2032;

    /* Ink */
    --ink: #f3f1ea;
    --ink-soft: #b7b9c9;
    --ink-faint: #7e8198;

    /* Lines */
    --line: rgba(255, 255, 255, 0.08);
    --line-strong: rgba(255, 255, 255, 0.16);

    /* Accent — electric "signal" lime */
    --signal: #cdf64a;
    --signal-dim: #add23a;
    --on-signal: #0a0b10;

    /* Secondary — violet (nods to the legacy brand, used as depth) */
    --violet: #8b6cff;
    --violet-2: #6d4dff;

    /* Type */
    --font-display: "Bricolage Grotesque", "Hanken Grotesk", system-ui, sans-serif;
    --font-body: "Hanken Grotesk", system-ui, -apple-system, "Segoe UI", sans-serif;
    --font-mono: "JetBrains Mono", ui-monospace, "SFMono-Regular", monospace;

    /* Rhythm */
    --maxw: 1140px;
    --radius: 16px;
    --radius-sm: 10px;
    --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: 6rem;
    -webkit-text-size-adjust: 100%;
}

body {
    margin: 0;
    font-family: var(--font-body);
    font-size: 1.0625rem;
    line-height: 1.6;
    color: var(--ink);
    background-color: var(--bg);
    background-image:
        radial-gradient(900px 520px at 78% -8%, rgba(139, 108, 255, 0.16), transparent 60%),
        radial-gradient(820px 520px at 6% -4%, rgba(205, 246, 74, 0.10), transparent 55%),
        linear-gradient(180deg, var(--bg-grad-top), var(--bg) 38%);
    background-repeat: no-repeat;
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
    overflow-x: hidden;
}

::selection {
    background: var(--signal);
    color: var(--on-signal);
}

a {
    color: var(--signal);
    text-decoration: none;
}

h1, h2, h3, h4 {
    font-family: var(--font-display);
    font-weight: 700;
    line-height: 1.04;
    letter-spacing: -0.02em;
    margin: 0;
    color: var(--ink);
}

p {
    margin: 0;
}

/* FocusOnNavigate moves focus to the h1 programmatically; suppress the ring. */
h1:focus {
    outline: none;
}

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

::-webkit-scrollbar {
    width: 12px;
    height: 12px;
}

::-webkit-scrollbar-track {
    background: var(--bg);
}

::-webkit-scrollbar-thumb {
    background: var(--surface-3);
    border: 3px solid var(--bg);
    border-radius: 99px;
}

::-webkit-scrollbar-thumb:hover {
    background: #2a3047;
}

/* ---------- Layout primitives ---------- */

.container {
    width: 100%;
    max-width: var(--maxw);
    margin-inline: auto;
    padding-inline: 1.5rem;
}

.site {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

main {
    flex: 1;
}

.section {
    padding-block: clamp(4rem, 9vw, 7.5rem);
    position: relative;
}

.section-head {
    max-width: 640px;
    margin-bottom: clamp(2rem, 5vw, 3.25rem);
}

.eyebrow {
    display: inline-flex;
    align-items: center;
    gap: 0.55rem;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 600;
    letter-spacing: 0.22em;
    text-transform: uppercase;
    color: var(--signal);
    margin: 0 0 1.1rem;
}

.eyebrow::before {
    content: "";
    width: 7px;
    height: 7px;
    border-radius: 50%;
    background: var(--signal);
    box-shadow: 0 0 0 4px rgba(205, 246, 74, 0.18);
}

.section h2 {
    font-size: clamp(1.9rem, 4.2vw, 3rem);
}

.section-head p {
    color: var(--ink-soft);
    font-size: 1.12rem;
    margin-top: 1rem;
}

/* ---------- Buttons ---------- */

.btn {
    --pad-y: 0.85rem;
    --pad-x: 1.5rem;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: var(--pad-y) var(--pad-x);
    font-family: var(--font-body);
    font-weight: 600;
    font-size: 0.98rem;
    line-height: 1;
    border-radius: 99px;
    border: 1px solid transparent;
    cursor: pointer;
    transition: transform 0.18s var(--ease), background-color 0.18s var(--ease),
        border-color 0.18s var(--ease), box-shadow 0.18s var(--ease), color 0.18s var(--ease);
    white-space: nowrap;
}

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

.btn:active {
    transform: translateY(0);
}

.btn-sm {
    --pad-y: 0.6rem;
    --pad-x: 1.05rem;
    font-size: 0.9rem;
}

.btn-lg {
    --pad-y: 1.05rem;
    --pad-x: 2rem;
    font-size: 1.05rem;
}

.btn-signal {
    background: var(--signal);
    color: var(--on-signal);
    box-shadow: 0 0 0 1px rgba(205, 246, 74, 0.4), 0 14px 40px -16px rgba(205, 246, 74, 0.55);
}

.btn-signal:hover {
    background: #d6ff5e;
    box-shadow: 0 0 0 1px rgba(205, 246, 74, 0.6), 0 18px 50px -14px rgba(205, 246, 74, 0.7);
}

.btn-ghost {
    background: rgba(255, 255, 255, 0.02);
    color: var(--ink);
    border-color: var(--line-strong);
}

.btn-ghost:hover {
    background: rgba(255, 255, 255, 0.06);
    border-color: rgba(255, 255, 255, 0.3);
}

.btn-arrow::after {
    content: "→";
    font-family: var(--font-mono);
    transition: transform 0.18s var(--ease);
}

.btn-arrow:hover::after {
    transform: translateX(4px);
}

/* ---------- Header ---------- */

.site-header {
    position: sticky;
    top: 0;
    z-index: 50;
    backdrop-filter: saturate(140%) blur(14px);
    background: rgba(10, 11, 16, 0.72);
    border-bottom: 1px solid var(--line);
}

.header-inner {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    height: 4.25rem;
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
    color: var(--ink);
    font-family: var(--font-display);
    font-weight: 800;
    font-size: 1.32rem;
    letter-spacing: -0.03em;
}

.brand-mark {
    width: 24px;
    height: 24px;
    display: block;
    object-fit: contain;
}

.site-nav {
    display: flex;
    align-items: center;
    gap: 1.75rem;
    margin-left: auto;
}

.site-nav a {
    color: var(--ink-soft);
    font-size: 0.95rem;
    font-weight: 500;
    transition: color 0.15s var(--ease);
}

.site-nav a:hover {
    color: var(--ink);
}

.header-cta {
    margin-left: 0.25rem;
}

/* ---------- Hero ---------- */

.hero {
    padding-block: clamp(3.5rem, 8vw, 6rem) clamp(3.5rem, 7vw, 5.5rem);
    position: relative;
}

.hero-grid {
    display: grid;
    grid-template-columns: 1.05fr 0.95fr;
    gap: clamp(2rem, 5vw, 4.5rem);
    align-items: center;
}

.hero h1 {
    font-size: clamp(2.6rem, 6.4vw, 4.6rem);
    font-weight: 800;
    letter-spacing: -0.035em;
}

.hero h1 .accent {
    color: var(--signal);
    position: relative;
}

.hero .lede {
    margin-top: 1.6rem;
    max-width: 36ch;
    font-size: 1.2rem;
    color: var(--ink-soft);
    line-height: 1.55;
}

.hero-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.9rem;
    margin-top: 2.2rem;
}

.hero-proof {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 1.25rem 1.75rem;
    margin-top: 2.6rem;
    padding-top: 1.8rem;
    border-top: 1px solid var(--line);
    font-family: var(--font-mono);
    font-size: 0.78rem;
    letter-spacing: 0.04em;
    color: var(--ink-faint);
    text-transform: uppercase;
}

.hero-proof span {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.hero-proof span::before {
    content: "";
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--signal);
}

/* Hero visual — a "today's lesson" card mock */
.lesson-card {
    position: relative;
    background: linear-gradient(180deg, var(--surface-2), var(--surface));
    border: 1px solid var(--line-strong);
    border-radius: var(--radius);
    padding: 1.5rem;
    box-shadow: 0 40px 90px -40px rgba(0, 0, 0, 0.9), 0 0 0 1px rgba(255, 255, 255, 0.02) inset;
}

.lesson-card::before {
    content: "";
    position: absolute;
    inset: -1px;
    border-radius: inherit;
    padding: 1px;
    background: linear-gradient(140deg, rgba(205, 246, 74, 0.5), transparent 35%, rgba(139, 108, 255, 0.45));
    -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
    -webkit-mask-composite: xor;
    mask-composite: exclude;
    pointer-events: none;
}

.lesson-card__top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 1.1rem;
}

.tag {
    font-family: var(--font-mono);
    font-size: 0.68rem;
    font-weight: 600;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--ink-soft);
    padding: 0.35rem 0.6rem;
    border: 1px solid var(--line-strong);
    border-radius: 99px;
}

.streak-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--signal);
}

.lesson-card__q {
    font-family: var(--font-display);
    font-weight: 600;
    font-size: 1.18rem;
    line-height: 1.25;
    letter-spacing: -0.01em;
    margin-bottom: 1rem;
}

.answer-line {
    font-size: 0.92rem;
    color: var(--ink-soft);
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--line);
    border-radius: var(--radius-sm);
    padding: 0.75rem 0.85rem;
    margin-bottom: 0.9rem;
}

.answer-line .cursor {
    display: inline-block;
    width: 2px;
    height: 1em;
    background: var(--signal);
    vertical-align: text-bottom;
    margin-left: 1px;
    animation: blink 1.1s steps(1) infinite;
}

.eval {
    display: flex;
    gap: 0.7rem;
    align-items: flex-start;
    background: rgba(205, 246, 74, 0.06);
    border: 1px solid rgba(205, 246, 74, 0.22);
    border-radius: var(--radius-sm);
    padding: 0.8rem 0.9rem;
}

.eval__badge {
    flex: none;
    width: 1.5rem;
    height: 1.5rem;
    border-radius: 50%;
    background: var(--signal);
    color: var(--on-signal);
    display: grid;
    place-items: center;
    font-size: 0.85rem;
    font-weight: 700;
}

.eval__body {
    font-size: 0.86rem;
    line-height: 1.45;
    color: var(--ink-soft);
}

.eval__body b {
    color: var(--ink);
    font-weight: 600;
}

.eval__meta {
    display: block;
    margin-top: 0.3rem;
    font-family: var(--font-mono);
    font-size: 0.68rem;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    color: var(--ink-faint);
}

/* ---------- Tracks ---------- */

.tracks-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.25rem;
}

.track {
    position: relative;
    overflow: hidden;
    padding: 2rem;
    border-radius: var(--radius);
    border: 1px solid var(--line-strong);
    background: linear-gradient(180deg, var(--surface), var(--bg));
    transition: transform 0.25s var(--ease), border-color 0.25s var(--ease);
}

.track:hover {
    transform: translateY(-4px);
    border-color: rgba(255, 255, 255, 0.28);
}

.track__glow {
    position: absolute;
    inset: auto -40% -60% auto;
    width: 70%;
    aspect-ratio: 1;
    border-radius: 50%;
    filter: blur(60px);
    opacity: 0.5;
    pointer-events: none;
}

.track--ai .track__glow {
    background: radial-gradient(circle, rgba(205, 246, 74, 0.45), transparent 70%);
}

.track--fin .track__glow {
    background: radial-gradient(circle, rgba(139, 108, 255, 0.5), transparent 70%);
}

.track--data .track__glow {
    background: radial-gradient(circle, rgba(74, 214, 246, 0.45), transparent 70%);
}

.track--sec .track__glow {
    background: radial-gradient(circle, rgba(246, 138, 74, 0.45), transparent 70%);
}

.track__no {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    letter-spacing: 0.16em;
    color: var(--ink-faint);
}

.track__level {
    color: var(--signal);
    font-weight: 600;
}

.track h3 {
    font-size: 1.55rem;
    margin: 0.8rem 0 0.7rem;
    position: relative;
}

.track p {
    color: var(--ink-soft);
    position: relative;
}

.track__tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.45rem;
    margin-top: 1.4rem;
    position: relative;
}

.track__tags span {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    color: var(--ink-soft);
    padding: 0.3rem 0.6rem;
    border-radius: 99px;
    border: 1px solid var(--line);
    background: rgba(255, 255, 255, 0.02);
}

/* ---------- How it works ---------- */

.steps {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.25rem;
    counter-reset: step;
}

.step {
    position: relative;
    padding: 1.9rem 1.6rem;
    border-radius: var(--radius);
    background: var(--surface);
    border: 1px solid var(--line);
}

.step__no {
    font-family: var(--font-mono);
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--signal);
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
    margin-bottom: 1.1rem;
}

.step__no::before {
    counter-increment: step;
    content: "0" counter(step);
}

.step__no::after {
    content: "";
    height: 1px;
    flex: 1;
    background: linear-gradient(90deg, var(--signal), transparent);
    opacity: 0.5;
}

.step h3 {
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
}

.step p {
    color: var(--ink-soft);
    font-size: 0.98rem;
}

/* ---------- Features ---------- */

.features-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.1rem;
}

.feature {
    display: flex;
    gap: 1.1rem;
    padding: 1.6rem;
    border-radius: var(--radius);
    border: 1px solid var(--line);
    background: linear-gradient(180deg, var(--surface), var(--bg));
    transition: border-color 0.2s var(--ease), background 0.2s var(--ease);
}

.feature:hover {
    border-color: var(--line-strong);
}

.feature__icon {
    flex: none;
    width: 2.6rem;
    height: 2.6rem;
    border-radius: 10px;
    display: grid;
    place-items: center;
    background: rgba(205, 246, 74, 0.1);
    border: 1px solid rgba(205, 246, 74, 0.25);
    color: var(--signal);
}

.feature__icon svg {
    width: 1.3rem;
    height: 1.3rem;
}

.feature h3 {
    font-size: 1.12rem;
    margin-bottom: 0.35rem;
}

.feature p {
    color: var(--ink-soft);
    font-size: 0.96rem;
}

/* ---------- Trust strip ---------- */

.trust {
    border-block: 1px solid var(--line);
    background: rgba(255, 255, 255, 0.015);
}

.trust-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1.5rem;
    padding-block: 2.75rem;
}

.trust-item {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}

.trust-item b {
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 1.05rem;
    color: var(--ink);
}

.trust-item span {
    font-size: 0.9rem;
    color: var(--ink-faint);
}

/* ---------- CTA band ---------- */

.cta {
    position: relative;
    overflow: hidden;
    border-radius: clamp(18px, 3vw, 28px);
    padding: clamp(2.75rem, 6vw, 4.75rem);
    text-align: center;
    background:
        radial-gradient(700px 320px at 50% -30%, rgba(205, 246, 74, 0.22), transparent 70%),
        linear-gradient(180deg, var(--surface-2), var(--surface));
    border: 1px solid var(--line-strong);
}

.cta h2 {
    font-size: clamp(2rem, 5vw, 3.2rem);
    max-width: 16ch;
    margin-inline: auto;
}

.cta p {
    color: var(--ink-soft);
    font-size: 1.12rem;
    max-width: 48ch;
    margin: 1.1rem auto 0;
}

.cta .hero-actions {
    justify-content: center;
}

.store-badges {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.75rem;
    margin-top: 1.6rem;
}

.store-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
    padding: 0.6rem 1rem;
    border-radius: 12px;
    border: 1px solid var(--line-strong);
    background: rgba(255, 255, 255, 0.02);
    color: var(--ink-soft);
    font-size: 0.82rem;
    cursor: not-allowed;
}

.store-badge small {
    display: block;
    font-family: var(--font-mono);
    font-size: 0.62rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--ink-faint);
}

.store-badge strong {
    color: var(--ink);
    font-weight: 600;
    font-size: 0.95rem;
}

/* ---------- Footer ---------- */

.site-footer {
    border-top: 1px solid var(--line);
    margin-top: 1rem;
    padding-block: 3.5rem 2.5rem;
    background: linear-gradient(180deg, transparent, rgba(0, 0, 0, 0.35));
}

.footer-top {
    display: grid;
    grid-template-columns: 1.4fr repeat(3, 1fr);
    gap: 2rem;
}

.footer-brand .brand {
    margin-bottom: 0.9rem;
}

.footer-brand p {
    color: var(--ink-faint);
    font-size: 0.92rem;
    max-width: 32ch;
}

.footer-col h4 {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    font-weight: 600;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--ink-faint);
    margin-bottom: 1rem;
}

.footer-col a {
    display: block;
    color: var(--ink-soft);
    font-size: 0.95rem;
    padding-block: 0.32rem;
    transition: color 0.15s var(--ease);
}

.footer-col a:hover {
    color: var(--signal);
}

.footer-bottom {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    margin-top: 3rem;
    padding-top: 1.6rem;
    border-top: 1px solid var(--line);
    font-size: 0.85rem;
    color: var(--ink-faint);
}

.footer-bottom .privacy {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    color: var(--signal);
}

/* ---------- About / prose pages ---------- */

.prose {
    max-width: 760px;
    padding-block: clamp(3.5rem, 8vw, 6rem);
}

.prose h1 {
    font-size: clamp(2.2rem, 5vw, 3.4rem);
    margin-bottom: 1.25rem;
}

.prose h2 {
    font-size: 1.5rem;
    margin: 2.75rem 0 1rem;
}

.prose p {
    color: var(--ink-soft);
    font-size: 1.1rem;
    margin-bottom: 1rem;
}

.prose ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    gap: 0.7rem;
}

.prose li {
    position: relative;
    padding-left: 1.6rem;
    color: var(--ink-soft);
}

.prose li::before {
    content: "";
    position: absolute;
    left: 0;
    top: 0.62em;
    width: 8px;
    height: 8px;
    border-radius: 2px;
    background: var(--signal);
}

.prose code {
    font-family: var(--font-mono);
    font-size: 0.88em;
    background: var(--surface-2);
    border: 1px solid var(--line);
    border-radius: 5px;
    padding: 0.1rem 0.4rem;
    color: var(--ink);
}

.prose-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.9rem;
    margin-top: 2.5rem;
}

/* ---------- Entrance animations ---------- */

@keyframes rise {
    from {
        opacity: 0;
        transform: translateY(22px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes blink {
    50% {
        opacity: 0;
    }
}

.reveal {
    opacity: 0;
    animation: rise 0.7s var(--ease) forwards;
}

.d1 { animation-delay: 0.05s; }
.d2 { animation-delay: 0.15s; }
.d3 { animation-delay: 0.25s; }
.d4 { animation-delay: 0.35s; }
.d5 { animation-delay: 0.45s; }
.d6 { animation-delay: 0.55s; }

/* ---------- Responsive ---------- */

@media (max-width: 920px) {
    .hero-grid {
        grid-template-columns: 1fr;
    }

    .hero-visual {
        order: -1;
        max-width: 460px;
    }

    .footer-top {
        grid-template-columns: 1fr 1fr;
    }

    .footer-brand {
        grid-column: 1 / -1;
    }

    .tracks-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 780px) {
    .site-nav {
        display: none;
    }

    .tracks-grid,
    .steps,
    .features-grid,
    .trust-grid {
        grid-template-columns: 1fr;
    }

    .trust-grid {
        gap: 1.75rem;
    }
}

@media (max-width: 540px) {
    body {
        font-size: 1rem;
    }

    .footer-top {
        grid-template-columns: 1fr;
        gap: 1.75rem;
    }

    .hero-actions .btn,
    .cta .hero-actions .btn {
        flex: 1 1 auto;
    }
}

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

    .reveal {
        opacity: 1;
        animation: none;
    }

    .answer-line .cursor {
        animation: none;
    }

    .btn:hover,
    .track:hover {
        transform: none;
    }
}

/* ---------- Track cards: explore link ---------- */

.track {
    isolation: isolate;
}

.track__glow {
    z-index: -1;
}

.track__link {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    margin-top: 1.5rem;
    font-family: var(--font-mono);
    font-size: 0.78rem;
    font-weight: 600;
    letter-spacing: 0.04em;
    color: var(--signal);
    transition: color 0.2s var(--ease);
}

.track__link::after {
    content: "";
    position: absolute;
    inset: 0;
    border-radius: var(--radius);
}

.track__link span {
    transition: transform 0.2s var(--ease);
}

.track:hover .track__link span {
    transform: translateX(3px);
}

/* ---------- Track detail page ---------- */

.track-hero {
    position: relative;
    overflow: hidden;
    isolation: isolate;
    padding-block: clamp(3rem, 7vw, 5.25rem) clamp(2rem, 4vw, 3rem);
    border-bottom: 1px solid var(--line);
    background: linear-gradient(180deg, var(--bg-grad-top), var(--bg));
}

.track-hero::before {
    content: "";
    position: absolute;
    z-index: -1;
    inset: -35% 25% auto -15%;
    width: 65%;
    aspect-ratio: 1;
    border-radius: 50%;
    filter: blur(85px);
    opacity: 0.4;
    pointer-events: none;
}

.track-hero.track--ai::before { background: radial-gradient(circle, rgba(205, 246, 74, 0.4), transparent 70%); }
.track-hero.track--fin::before { background: radial-gradient(circle, rgba(139, 108, 255, 0.45), transparent 70%); }
.track-hero.track--data::before { background: radial-gradient(circle, rgba(74, 214, 246, 0.4), transparent 70%); }
.track-hero.track--sec::before { background: radial-gradient(circle, rgba(246, 138, 74, 0.4), transparent 70%); }

.track-back {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    font-family: var(--font-mono);
    font-size: 0.74rem;
    font-weight: 600;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--ink-faint);
    margin-bottom: 1.5rem;
    transition: color 0.2s var(--ease);
}

.track-back:hover {
    color: var(--ink-soft);
}

.track-hero h1 {
    font-size: clamp(2.2rem, 5.5vw, 3.6rem);
    line-height: 1.04;
    letter-spacing: -0.02em;
    margin: 0.5rem 0 0;
    max-width: 20ch;
}

.track-hero__tagline {
    font-size: clamp(1.1rem, 2.4vw, 1.4rem);
    color: var(--ink);
    max-width: 54ch;
    margin: 1.1rem 0 0;
    line-height: 1.4;
}

.track-hero__intro {
    color: var(--ink-soft);
    max-width: 60ch;
    margin: 1.3rem 0 0;
    line-height: 1.6;
}

.track-hero .hero-actions {
    margin-top: 2rem;
}

.track-detail-grid {
    display: grid;
    grid-template-columns: 1fr 0.82fr;
    gap: clamp(2rem, 5vw, 4rem);
    align-items: start;
}

.track-detail-main h2 {
    font-size: clamp(1.4rem, 3vw, 1.95rem);
    margin: 0 0 1.4rem;
}

.outcomes + h2 {
    margin-top: 2.75rem;
}

.outcomes {
    list-style: none;
    display: grid;
    gap: 0.9rem;
    margin: 0;
    padding: 0;
}

.outcomes li {
    position: relative;
    padding-left: 2.1rem;
    color: var(--ink-soft);
    line-height: 1.5;
}

.outcomes li::before {
    content: "";
    position: absolute;
    left: 0;
    top: 0.05rem;
    width: 1.35rem;
    height: 1.35rem;
    border-radius: 50%;
    background: rgba(205, 246, 74, 0.14);
    border: 1px solid rgba(205, 246, 74, 0.4);
}

.outcomes li::after {
    content: "\2713";
    position: absolute;
    left: 0.34rem;
    top: 0.02rem;
    font-size: 0.82rem;
    font-weight: 700;
    color: var(--signal);
}

.syllabus {
    list-style: none;
    margin: 0;
    padding: 0;
}

.syllabus__item {
    display: flex;
    gap: 1.1rem;
    padding: 1.25rem 0;
    border-top: 1px solid var(--line);
}

.syllabus__item:last-child {
    border-bottom: 1px solid var(--line);
}

.syllabus__no {
    flex: none;
    min-width: 2ch;
    padding-top: 0.15rem;
    font-family: var(--font-mono);
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--signal);
}

.syllabus__body h3 {
    font-size: 1.12rem;
    margin: 0 0 0.35rem;
}

.syllabus__body p {
    color: var(--ink-soft);
    font-size: 0.95rem;
    line-height: 1.5;
    margin: 0;
}

.track-detail-aside {
    position: sticky;
    top: 2rem;
    display: grid;
    gap: 1.2rem;
}

.track-aside-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.45rem;
}

.track-aside-tags span {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    color: var(--ink-soft);
    padding: 0.35rem 0.65rem;
    border-radius: 99px;
    border: 1px solid var(--line);
    background: rgba(255, 255, 255, 0.02);
}

@media (max-width: 920px) {
    .track-detail-grid {
        grid-template-columns: 1fr;
    }

    .track-detail-aside {
        position: static;
        order: -1;
        max-width: 460px;
    }
}

@media (prefers-reduced-motion: reduce) {
    .track:hover .track__link span {
        transform: none;
    }
}

/* ---------- Subscribe / pricing plans ---------- */

/* Each .plan is a .track card with extra room for price + features + an inline form.
   .plans-grid is .tracks-grid with a wider gap so the inline forms breathe. */
.plans-grid {
    gap: 1.6rem;
    margin-bottom: 1.5rem;
}

.plan {
    display: flex;
    flex-direction: column;
    gap: 1.1rem;
}

.plan--featured {
    border-color: rgba(205, 246, 74, 0.45);
    box-shadow: 0 0 0 1px rgba(205, 246, 74, 0.18) inset;
}

.plan-price {
    display: flex;
    align-items: baseline;
    gap: 0.5rem;
    margin: 0.2rem 0 0.4rem;
    position: relative;
}

.plan-price__num {
    font-family: var(--font-display);
    font-size: 2.6rem;
    font-weight: 700;
    color: var(--ink);
    line-height: 1;
}

.plan-price__unit {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--ink-soft);
    letter-spacing: 0.04em;
}

.plan-features {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 0.55rem;
    color: var(--ink-soft);
    font-size: 0.95rem;
    position: relative;
}

.plan-features li {
    position: relative;
    padding-left: 1.4rem;
}

.plan-features li::before {
    content: "";
    position: absolute;
    left: 0.1rem;
    top: 0.55em;
    width: 0.55rem;
    height: 0.55rem;
    border-radius: 50%;
    background: var(--signal);
    box-shadow: 0 0 0 3px rgba(205, 246, 74, 0.18);
}

.plan-form {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-top: auto;            /* push form to the bottom of the card */
    padding-top: 1rem;
    border-top: 1px solid var(--line);
    position: relative;
}

.plan-form__label {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--ink-faint);
}

.plan-form__input {
    width: 100%;
    padding: 0.75rem 0.9rem;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--line-strong);
    border-radius: 10px;
    color: var(--ink);
    font: inherit;
    font-size: 0.98rem;
    transition: border-color 0.18s var(--ease), background 0.18s var(--ease);
}

.plan-form__input::placeholder {
    color: var(--ink-faint);
}

.plan-form__input:focus {
    outline: none;
    border-color: var(--signal);
    background: rgba(205, 246, 74, 0.04);
}

.plan-form__cta {
    margin-top: 0.4rem;
    width: 100%;
    justify-content: center;
}

.subscribe-error {
    border: 1px solid rgba(246, 138, 74, 0.45);
    background: rgba(246, 138, 74, 0.06);
    color: var(--ink);
    padding: 1rem 1.2rem;
    border-radius: var(--radius);
    margin-bottom: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
    font-size: 0.95rem;
}

.subscribe-error strong {
    font-family: var(--font-display);
    font-weight: 700;
    color: var(--ink);
}

.subscribe-error span {
    color: var(--ink-soft);
}

.plans-footnote {
    margin-top: 1.5rem;
    color: var(--ink-faint);
    font-size: 0.88rem;
    text-align: center;
    max-width: 60ch;
    margin-inline: auto;
}

.plans-footnote a {
    color: var(--ink-soft);
    text-decoration: underline;
    text-underline-offset: 3px;
}

/* ---------- Library cards ---------- */

/* A library card reuses .track styling but is itself the anchor — the whole card is clickable. */
a.track.library-card {
    color: inherit;
    text-decoration: none;
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
}

a.track.library-card:hover {
    border-color: var(--signal);
}

.library-card__cta {
    margin-top: auto;
    padding-top: 0.8rem;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--signal);
    letter-spacing: 0.04em;
}

/* Header sign-out button — quiet, secondary to the "Your library" CTA */
.header-signout {
    margin: 0;
    padding: 0;
}

.header-signout__btn {
    background: none;
    border: none;
    padding: 0.4rem 0.6rem;
    color: var(--ink-soft);
    font: inherit;
    font-size: 0.88rem;
    cursor: pointer;
    transition: color 0.15s var(--ease);
}

.header-signout__btn:hover {
    color: var(--ink);
}

.header-signin {
    color: var(--ink-soft);
    text-decoration: none;
    font-size: 0.92rem;
    padding: 0.4rem 0.6rem;
    transition: color 0.15s var(--ease);
}

.header-signin:hover {
    color: var(--ink);
}

/* ---------- Module overview (lesson list) ---------- */

.lesson-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
}

.lesson-list__item {
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: linear-gradient(180deg, var(--surface), var(--bg));
    transition: border-color 0.2s var(--ease), transform 0.2s var(--ease);
}

.lesson-list__item:hover {
    border-color: var(--signal);
    transform: translateY(-2px);
}

.lesson-list__link {
    display: flex;
    align-items: center;
    gap: 1.4rem;
    padding: 1.2rem 1.6rem;
    color: inherit;
    text-decoration: none;
}

.lesson-list__no {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--ink-faint);
    letter-spacing: 0.16em;
    flex: none;
}

.lesson-list__body {
    flex: 1;
    min-width: 0;
}

.lesson-list__body h3 {
    margin: 0 0 0.2rem;
    font-size: 1.2rem;
}

.lesson-list__meta {
    margin: 0;
    color: var(--ink-faint);
    font-size: 0.88rem;
    font-family: var(--font-mono);
}

.lesson-list__arrow {
    color: var(--signal);
    font-size: 1.4rem;
    flex: none;
}

/* ---------- Lesson reader ---------- */

.lesson-blocks > .container {
    max-width: 64ch;
}

.block {
    margin: 0 0 1.6rem;
}

.block--text {
    color: var(--ink);
    font-size: 1.06rem;
    line-height: 1.65;
}

.block--text p {
    margin: 0 0 1em;
}

.block--text h2,
.block--text h3,
.block--text h4 {
    color: var(--ink);
    margin: 1.5em 0 0.5em;
    line-height: 1.25;
}

.block--text h2 { font-size: 1.4rem; }
.block--text h3 { font-size: 1.2rem; }
.block--text h4 { font-size: 1.05rem; }

.block--text h2:first-child,
.block--text h3:first-child {
    margin-top: 0;
}

.block--text ul,
.block--text ol {
    margin: 0 0 1em;
    padding-left: 1.4em;
}

.block--text li {
    margin-bottom: 0.35em;
}

.block--text a {
    color: var(--signal);
    text-decoration: underline;
    text-underline-offset: 3px;
}

.block--text a:hover {
    color: var(--signal-dim);
}

.block--text blockquote {
    margin: 1em 0;
    padding-left: 1em;
    border-left: 3px solid var(--line-strong);
    color: var(--ink-soft);
}

.block--text table {
    width: 100%;
    border-collapse: collapse;
    margin: 1em 0;
    font-size: 0.95em;
}

.block--text th,
.block--text td {
    border-bottom: 1px solid var(--line);
    padding: 0.5em 0.7em;
    text-align: left;
}

.block--text th {
    color: var(--ink);
    font-weight: 600;
}

.block--text pre {
    background: rgba(0, 0, 0, 0.45);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 1rem 1.2rem;
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: 0.92rem;
    line-height: 1.5;
}

.block--text pre code {
    background: transparent;
    padding: 0;
}

/* Markdig task lists — <ul class="contains-task-list"> + <li class="task-list-item"> */
.block--text .contains-task-list {
    list-style: none;
    padding-left: 0;
}

.block--text .task-list-item {
    padding-left: 1.6em;
    position: relative;
}

.block--text .task-list-item input[type="checkbox"] {
    position: absolute;
    left: 0;
    top: 0.35em;
    margin: 0;
    accent-color: var(--signal);
}

.block--text code,
.block--free-response code,
.block--choice code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background: rgba(255, 255, 255, 0.06);
    padding: 0.1em 0.35em;
    border-radius: 4px;
}

.block--callout {
    border-left: 3px solid var(--ink-faint);
    background: rgba(255, 255, 255, 0.03);
    padding: 1rem 1.2rem;
    border-radius: 0 var(--radius) var(--radius) 0;
}

.block--callout p {
    margin: 0 0 0.6em;
}

.block--callout p:last-child {
    margin-bottom: 0;
}

.block--callout--info {
    border-left-color: rgba(74, 214, 246, 0.7);
    background: rgba(74, 214, 246, 0.05);
}

.block--callout--warn {
    border-left-color: rgba(246, 138, 74, 0.7);
    background: rgba(246, 138, 74, 0.05);
}

.block--callout--key {
    border-left-color: var(--signal);
    background: rgba(205, 246, 74, 0.06);
}

.block--image img {
    max-width: 100%;
    border-radius: var(--radius);
    border: 1px solid var(--line);
}

.block--image figcaption {
    color: var(--ink-faint);
    font-size: 0.88rem;
    margin-top: 0.5rem;
    text-align: center;
}

.block--code {
    background: rgba(0, 0, 0, 0.45);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 1rem 1.2rem;
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: 0.92rem;
    line-height: 1.5;
}

.block--code code {
    background: transparent;
    padding: 0;
    color: var(--ink);
}

.block--choice,
.block--free-response {
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 1.4rem 1.6rem;
}

.block__prompt {
    font-size: 1.08rem;
    margin: 0 0 0.9rem;
    color: var(--ink);
}

.block__hint {
    color: var(--ink-faint);
    font-size: 0.9rem;
    margin: 0.6rem 0 0;
}

.choice-options {
    list-style: none;
    padding: 0;
    margin: 0 0 1rem;
    counter-reset: choice;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.choice-option {
    counter-increment: choice;
    padding: 0.7rem 1rem 0.7rem 2.6rem;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--line);
    border-radius: 10px;
    position: relative;
    color: var(--ink);
}

.choice-option::before {
    content: counter(choice, upper-alpha);
    position: absolute;
    left: 0.9rem;
    top: 0.7rem;
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--ink-faint);
}

.choice-reveal {
    margin-top: 0.6rem;
}

.choice-reveal summary {
    cursor: pointer;
    color: var(--signal);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    letter-spacing: 0.04em;
}

.choice-reveal__body {
    margin-top: 0.7rem;
    padding-top: 0.7rem;
    border-top: 1px dashed var(--line);
}

.choice-reveal__explanation {
    color: var(--ink-soft);
}

/* ---------- Lesson navigation ---------- */

.lesson-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.lesson-nav .lesson-nav__prev,
.lesson-nav .lesson-nav__next {
    max-width: 48%;
}

@media (max-width: 600px) {
    .lesson-nav .lesson-nav__prev,
    .lesson-nav .lesson-nav__next {
        max-width: 100%;
        width: 100%;
    }
}

/* ---------- Streak + completion UI ---------- */

.streak-banner {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    font-family: var(--font-mono);
    font-size: 0.82rem;
    letter-spacing: 0.06em;
    color: var(--signal);
    background: rgba(205, 246, 74, 0.08);
    border: 1px solid rgba(205, 246, 74, 0.25);
    border-radius: 6px;
    padding: 0.3rem 0.75rem;
    margin-bottom: 1.5rem;
}

.lesson-list__check {
    color: var(--signal);
    font-size: 1rem;
    flex: none;
    line-height: 1;
}

.lesson-completion-count {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--ink-faint);
    letter-spacing: 0.06em;
    margin-top: 0.25rem;
}

.mark-complete-form {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
    padding: 2rem 0 1rem;
}

.completed-banner {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-family: var(--font-mono);
    font-size: 0.88rem;
    letter-spacing: 0.05em;
    color: var(--signal);
    background: rgba(205, 246, 74, 0.08);
    border: 1px solid rgba(205, 246, 74, 0.25);
    border-radius: 8px;
    padding: 0.6rem 1.2rem;
    margin: 0 auto 1rem;
}
}