:root {
    --bg: #f3f7fb;
    --panel: #ffffff;
    --ink: #183153;
    --muted: #58708e;
    --line: rgba(24, 49, 83, 0.14);
    --accent: #0f5f80;
    --accent-dark: #0b4d69;
    --accent-soft: rgba(15, 95, 128, 0.1);
    --green: #1f8f69;
    --paypal-blue: #003087;
    --paypal-light: #009cde;
    --paypal-gold: #ffc439;
    --shadow: 0 18px 42px rgba(14, 41, 68, 0.1);
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: "Segoe UI", system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg);
    color: var(--ink);
    line-height: 1.55;
    overflow-x: hidden;
}

a {
    color: inherit;
}

.shell {
    width: min(1120px, 92vw);
    margin: 0 auto;
    padding: 32px 0 48px;
}

.topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    margin-bottom: 16px;
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    color: var(--accent);
    font-weight: 800;
    text-decoration: none;
}

.brand-mark {
    display: inline-grid;
    width: 34px;
    height: 34px;
    place-items: center;
    border-radius: 8px;
    background: var(--accent);
    color: #fff;
}

.page-nav {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
    justify-content: flex-end;
}

.nav-link,
.language-switch button {
    min-height: 38px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--panel);
    color: var(--ink);
    cursor: pointer;
    font: inherit;
    font-size: 14px;
    font-weight: 700;
    padding: 8px 12px;
    text-decoration: none;
}

.language-switch {
    display: inline-flex;
    padding: 4px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--panel);
    box-shadow: 0 8px 20px rgba(14, 41, 68, 0.06);
}

.language-switch button {
    min-width: 48px;
    border: 0;
    border-radius: 6px;
    background: transparent;
    color: var(--muted);
    font-weight: 800;
}

.language-switch button[aria-pressed="true"] {
    background: var(--accent);
    color: #fff;
}

.nav-label-short {
    display: none;
}

.hero,
.panel {
    min-width: 0;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--panel);
    box-shadow: var(--shadow);
}

.hero {
    padding: 36px;
}

.hero.split {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(280px, 360px);
    gap: 28px;
    align-items: center;
}

.eyebrow {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 6px 10px;
    border-radius: 999px;
    background: var(--accent-soft);
    color: var(--accent);
    font-size: 13px;
    font-weight: 800;
    text-transform: uppercase;
}

h1 {
    margin: 16px 0 10px;
    font-size: 42px;
    line-height: 1.12;
}

.page-title {
    font-size: 34px;
}

.lead {
    max-width: 980px;
    margin: 0;
    color: var(--muted);
    font-size: 18px;
    line-height: 1.55;
}

.actions {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-top: 28px;
}

.button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 42px;
    padding: 10px 16px;
    border: 1px solid var(--line);
    border-radius: 6px;
    background: #fff;
    color: var(--ink);
    font-weight: 700;
    text-decoration: none;
}

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

.button-guide,
.button-demo,
.button-sample,
.button-support {
    border-color: transparent;
    color: #fff;
}

.button-guide {
    background: #0f5f80;
}

.button-demo {
    background: #1f8f69;
}

.button-sample {
    background: #b56a18;
}

.button-support {
    background: #5f4bb6;
}

.button:hover,
.tile:hover {
    border-color: rgba(15, 95, 128, 0.5);
    box-shadow: 0 10px 24px rgba(14, 41, 68, 0.08);
}

.grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 16px;
    margin-top: 20px;
}

.tile,
.card {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--panel);
    color: inherit;
    text-decoration: none;
}

.tile {
    min-height: 164px;
    padding: 20px;
}

.card {
    display: block;
    min-height: 190px;
    padding: 22px;
}

.tile h2,
.card h2,
.card h3 {
    margin: 0 0 8px;
    font-size: 20px;
    line-height: 1.25;
}

.tile p,
.card p,
.section p {
    margin: 0;
    color: var(--muted);
}

.status {
    display: inline-flex;
    margin-top: 14px;
    color: var(--green);
    font-size: 14px;
    font-weight: 700;
}

.section {
    padding: 34px 0 0;
}

.section h2 {
    margin: 0 0 12px;
    font-size: 30px;
}

.content {
    display: grid;
    gap: 18px;
    margin-top: 20px;
}

.content .panel {
    padding: 24px;
}

.content h2 {
    margin: 0 0 12px;
    font-size: 26px;
    line-height: 1.22;
}

.content h3 {
    margin: 20px 0 8px;
    font-size: 20px;
}

.content p,
.content li {
    color: var(--muted);
}

.content p {
    margin: 0 0 12px;
}

.content ol,
.content ul {
    margin: 0;
    padding-left: 22px;
}

.content li + li {
    margin-top: 8px;
}

.code-block {
    max-width: 100%;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    margin: 14px 0;
    padding: 14px 16px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #0f1b2a;
    color: #edf6ff;
    font: 14px/1.6 Consolas, "Liberation Mono", Menlo, monospace;
}

.code-block code {
    white-space: pre;
}

.callout {
    min-width: 0;
    margin-top: 14px;
    padding: 14px 16px;
    border: 1px solid rgba(15, 95, 128, 0.24);
    border-radius: 8px;
    background: var(--accent-soft);
    color: var(--ink);
}

.callout p {
    margin: 0;
    color: var(--ink);
}

.guide-figure {
    margin: 18px 0 0;
}

.guide-figure img {
    display: block;
    width: 100%;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #e9eff6;
}

.guide-figure figcaption {
    margin-top: 8px;
    color: var(--muted);
    font-size: 14px;
}

.guide-steps {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
    margin-top: 16px;
}

.guide-step {
    padding: 16px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #fff;
}

.guide-step strong {
    display: block;
    margin-bottom: 6px;
    color: var(--ink);
}

.paypal-card {
    position: relative;
    overflow: hidden;
    padding: 24px;
}

.paypal-card::before {
    content: "";
    position: absolute;
    inset: 0 0 auto;
    height: 8px;
    background: linear-gradient(90deg, var(--paypal-blue), var(--paypal-light), var(--paypal-gold));
}

.paypal-logo {
    display: inline-flex;
    align-items: baseline;
    gap: 0;
    margin-bottom: 16px;
    color: var(--paypal-blue);
    font-size: 30px;
    font-weight: 900;
    letter-spacing: 0;
}

.paypal-logo span {
    color: var(--paypal-light);
}

.amount {
    display: flex;
    align-items: baseline;
    gap: 8px;
    margin: 14px 0 8px;
    color: var(--ink);
    font-size: 52px;
    font-weight: 900;
    line-height: 1;
}

.amount small {
    color: var(--muted);
    font-size: 18px;
    font-weight: 800;
}

.note {
    margin: 18px 0 0;
    color: var(--muted);
    font-size: 14px;
}

.footer {
    margin-top: 28px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    flex-wrap: wrap;
    color: var(--muted);
    font-size: 14px;
}

.footer-home-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 40px;
    padding: 9px 14px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--panel);
    color: var(--ink);
    font-weight: 800;
    text-decoration: none;
    box-shadow: var(--shadow);
}

.footer-home-link:hover,
.footer-home-link:focus-visible {
    color: var(--accent);
    border-color: rgba(16, 104, 132, 0.3);
}

.footer-home-link:focus-visible {
    outline: 3px solid rgba(16, 104, 132, 0.18);
    outline-offset: 3px;
}

.back-to-top {
    position: fixed;
    right: 24px;
    bottom: 24px;
    z-index: 50;
    width: 48px;
    height: 48px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border: 1px solid rgba(255, 255, 255, 0.72);
    border-radius: 999px;
    background: var(--accent);
    color: #ffffff;
    box-shadow: 0 16px 34px rgba(16, 104, 132, 0.28);
    cursor: pointer;
    font-size: 24px;
    font-weight: 900;
    line-height: 1;
    opacity: 0;
    pointer-events: none;
    transform: translateY(10px);
    transition: opacity 160ms ease, transform 160ms ease, background 160ms ease;
}

.back-to-top:hover,
.back-to-top:focus-visible {
    background: var(--accent-dark);
    transform: translateY(6px);
}

.back-to-top:focus-visible {
    outline: 3px solid rgba(16, 104, 132, 0.24);
    outline-offset: 3px;
}

.back-to-top.is-visible {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
}

@media (max-width: 860px) {
    .shell {
        padding: 20px 0 28px;
    }

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

    .page-nav {
        justify-content: flex-start;
    }

    .nav-label-full {
        display: none;
    }

    .nav-label-short {
        display: inline;
    }

    .hero,
    .hero.split {
        grid-template-columns: 1fr;
        padding: 24px;
    }

    .content .panel {
        padding: 20px;
    }

    h1,
    .page-title {
        font-size: 32px;
    }

    .content h2 {
        font-size: 23px;
    }

    .code-block {
        padding: 12px;
        font-size: 13px;
    }

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

    .guide-steps {
        grid-template-columns: 1fr;
    }

    .back-to-top {
        right: 16px;
        bottom: 16px;
        width: 44px;
        height: 44px;
        font-size: 22px;
    }

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

@media (max-width: 520px) {
    .shell {
        width: min(100% - 24px, 1120px);
    }

    .hero {
        padding: 20px;
    }

    .content .panel {
        padding: 18px;
    }

    h1,
    .page-title {
        font-size: 28px;
    }

    .lead {
        font-size: 16px;
    }

    .content h2 {
        font-size: 21px;
    }

    .content h3 {
        font-size: 18px;
    }

    .code-block {
        padding: 10px;
        font-size: 12px;
    }
}