:root {
    --ink: #17212b;
    --muted: #64748b;
    --line: #d8dee8;
    --panel: #ffffff;
    --bg: #f3f6f8;
    --accent: #087f8c;
    --accent-dark: #066572;
    --good: #0f8a5f;
    --bad: #bf3d3d;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    color: var(--ink);
    background: var(--bg);
}

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

main {
    width: min(1120px, calc(100% - 32px));
    margin: 0 auto;
}

.topbar {
    position: sticky;
    top: 0;
    z-index: 50;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 22px;
    padding: 14px clamp(16px, 4vw, 48px);
    background: rgba(255, 255, 255, 0.94);
    border-bottom: 1px solid var(--line);
    box-shadow: 0 10px 30px rgba(23, 33, 43, 0.08);
    backdrop-filter: blur(14px);
}

.brand {
    color: var(--ink);
    display: inline-flex;
    align-items: center;
    gap: 12px;
    min-width: max-content;
}

.brand-mark {
    width: 42px;
    height: 42px;
    border-radius: 10px;
    display: inline-grid;
    place-items: center;
    background: linear-gradient(135deg, var(--accent), #1f9f82);
    color: #ffffff;
    font-weight: 900;
    letter-spacing: 0;
    box-shadow: 0 10px 22px rgba(8, 127, 140, 0.22);
}

.brand strong {
    display: block;
    font-size: 20px;
    line-height: 1.05;
}

.brand small {
    display: block;
    margin-top: 3px;
    color: var(--muted);
    font-size: 12px;
    font-weight: 700;
}

.main-nav,
nav {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.main-nav a {
    color: #334155;
    border-radius: 999px;
    padding: 10px 13px;
    font-weight: 800;
    transition: background 0.2s, color 0.2s, transform 0.2s;
}

.main-nav a:hover {
    background: #e8f5f4;
    color: var(--accent-dark);
    transform: translateY(-1px);
}

.main-nav .nav-pill {
    background: var(--accent);
    color: #ffffff;
    box-shadow: 0 10px 20px rgba(8, 127, 140, 0.18);
}

.main-nav .nav-pill:hover {
    background: var(--accent-dark);
    color: #ffffff;
}

.main-nav .nav-pill.muted {
    background: #eef2f6;
    color: #334155;
    box-shadow: none;
}

.button,
button {
    border: 0;
    border-radius: 6px;
    background: var(--accent);
    color: #ffffff;
    padding: 11px 16px;
    font-weight: 700;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.button:hover,
button:hover {
    background: var(--accent-dark);
}

.button.small {
    padding: 8px 12px;
}

.button.ghost {
    background: #e7edf1;
    color: var(--ink);
}

.hero,
.page-head {
    display: flex;
    justify-content: space-between;
    gap: 24px;
    align-items: center;
    padding: 46px 0 28px;
}

.hero h1,
.page-head h1 {
    margin: 0;
    max-width: 760px;
    font-size: clamp(30px, 5vw, 56px);
    line-height: 1.02;
}

.hero p {
    max-width: 680px;
    color: var(--muted);
    font-size: 18px;
}

.eyebrow {
    margin: 0 0 8px;
    color: var(--accent);
    text-transform: uppercase;
    font-size: 13px;
    font-weight: 800;
}

.test-shell {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 260px;
    gap: 18px;
    align-items: start;
}

.panel {
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 8px;
    padding: 22px;
}

.test-meta {
    display: grid;
    grid-template-columns: 1fr 180px;
    gap: 14px;
    margin-bottom: 16px;
}

label {
    display: grid;
    gap: 7px;
    color: var(--muted);
    font-weight: 700;
}

input,
select,
textarea {
    width: 100%;
    border: 1px solid var(--line);
    border-radius: 6px;
    padding: 12px;
    font: inherit;
    color: var(--ink);
    background: #ffffff;
}

.sample-text {
    padding: 18px;
    border-radius: 8px;
    background: #eef6f5;
    line-height: 1.7;
    font-size: 18px;
}

textarea {
    min-height: 180px;
    margin-top: 16px;
    resize: vertical;
    line-height: 1.6;
}

.actions {
    display: flex;
    gap: 10px;
    margin-top: 14px;
}

.stats {
    display: grid;
    gap: 12px;
}

.stats div {
    background: #ffffff;
    border: 1px solid var(--line);
    border-radius: 8px;
    padding: 18px;
}

.stats strong {
    display: block;
    font-size: 34px;
}

.stats span {
    color: var(--muted);
}

#resultMessage {
    line-height: 1.5;
    font-weight: 700;
}

.auth {
    min-height: 65vh;
    display: grid;
    place-items: center;
}

.form {
    width: min(420px, 100%);
    display: grid;
    gap: 16px;
}

.form h1,
.panel h2 {
    margin-top: 0;
}

.alert {
    margin: 0;
    border-radius: 6px;
    padding: 12px;
    background: #fff0f0;
    color: var(--bad);
}

.table-wrap {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
}

th,
td {
    text-align: left;
    padding: 13px;
    border-bottom: 1px solid var(--line);
}

.badge {
    border-radius: 999px;
    padding: 5px 10px;
    font-size: 13px;
    font-weight: 800;
}

.badge.pass {
    color: var(--good);
    background: #e8f7f0;
}

.badge.fail {
    color: var(--bad);
    background: #fff0f0;
}

.certificate {
    padding: 44px 0;
}

.certificate-box {
    background: #ffffff;
    border: 10px solid #d7c589;
    outline: 2px solid #8d793a;
    padding: clamp(28px, 6vw, 70px);
    text-align: center;
}

.certificate-box h1 {
    font-size: clamp(38px, 7vw, 72px);
    margin: 10px 0;
}

.certificate-stats {
    display: flex;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
    margin: 26px 0;
}

.certificate-stats span {
    border: 1px solid var(--line);
    border-radius: 6px;
    padding: 10px 14px;
}

.tutorial-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 16px;
    padding-bottom: 40px;
}

.seo-landing {
    padding: 34px 0 12px;
}

.seo-hero {
    background: linear-gradient(135deg, #ffffff 0%, #ecf7f6 100%);
    border: 1px solid var(--line);
    border-radius: 12px;
    padding: clamp(24px, 5vw, 48px);
    box-shadow: 0 14px 36px rgba(23, 33, 43, 0.08);
}

.seo-hero h1 {
    max-width: 820px;
    margin: 0;
    font-size: clamp(32px, 5vw, 54px);
    line-height: 1.05;
}

.seo-hero p {
    max-width: 760px;
    color: var(--muted);
    font-size: 18px;
    line-height: 1.7;
}

.seo-link-strip {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    margin: 18px 0;
}

.seo-link-strip a {
    border: 1px solid var(--line);
    border-radius: 999px;
    padding: 9px 13px;
    background: #ffffff;
    font-weight: 800;
}

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

.seo-panel {
    margin-bottom: 16px;
}

.seo-panel h2 {
    margin: 0 0 10px;
    font-size: 24px;
}

.seo-panel p,
.seo-panel li {
    color: #334155;
    line-height: 1.75;
}

.seo-check-list {
    margin: 12px 0 0;
    padding-left: 20px;
}

.seo-faq {
    display: grid;
    gap: 10px;
}

.seo-faq details {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #f8fbfc;
    padding: 14px 16px;
}

.seo-faq summary {
    cursor: pointer;
    font-weight: 800;
}

.footer {
    width: min(1120px, calc(100% - 32px));
    margin: 36px auto 22px;
    color: var(--muted);
}

.footer-grid {
    display: grid;
    grid-template-columns: minmax(0, 1.4fr) 1fr 1fr;
    gap: 24px;
    padding: 26px;
    background: #ffffff;
    border: 1px solid var(--line);
    border-radius: 12px;
}

.footer strong {
    display: block;
    color: var(--ink);
    margin-bottom: 10px;
}

.footer p {
    margin: 0 0 10px;
    line-height: 1.6;
}

.footer a {
    display: block;
    margin: 8px 0;
}

.footer-bottom {
    padding: 16px 0 0;
    text-align: center;
}

@media (max-width: 760px) {
    .topbar,
    .hero,
    .page-head {
        align-items: flex-start;
        flex-direction: column;
    }

    .test-shell,
    .test-meta,
    .tutorial-grid,
    .seo-content-grid,
    .footer-grid {
        grid-template-columns: 1fr;
    }

    .brand small {
        display: none;
    }

    .main-nav {
        width: 100%;
    }

    .main-nav a {
        padding: 9px 11px;
    }
}

@media print {
    .topbar,
    .footer,
    .certificate .button {
        display: none;
    }

    body {
        background: #ffffff;
    }
}