:root {
    --bg: #ffffff;
    --page: #ffffff;
    --panel: #ffffff;
    --soft-panel: #f7f8fa;
    --text: #1f2933;
    --muted: #5f6f7f;
    --link: #1f5f8b;
    --link-hover: #153f5c;
    --line: #d8dee4;
    --strong-line: #c3ccd5;
    --button-bg: #1f5f8b;
    --button-text: #ffffff;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: auto;
}

body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.65;
    font-size: 16px;
}

a {
    color: var(--link);
    text-decoration: underline;
    text-underline-offset: 2px;
}

a:hover,
a:focus {
    color: var(--link-hover);
}

.wrap {
    width: min(1080px, calc(100% - 32px));
    margin: 0 auto;
}

.site-header {
    border-bottom: 1px solid var(--line);
    background: var(--page);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
    padding: 18px 0;
}

.brand {
    display: grid;
    gap: 2px;
    color: var(--text);
    min-width: 220px;
    text-decoration: none;
}

.brand:hover,
.brand:focus {
    text-decoration: none;
    color: var(--text);
}

.brand-title {
    font-weight: 700;
    letter-spacing: 0.01em;
    font-size: 1.15rem;
}

.brand-subtitle {
    color: var(--muted);
    font-size: 0.86rem;
}

.main-nav {
    display: flex;
    flex-wrap: wrap;
    justify-content: flex-end;
    gap: 4px 10px;
}

.main-nav a {
    color: var(--link);
    padding: 5px 6px;
    font-size: 0.95rem;
    text-decoration: none;
    border-bottom: 2px solid transparent;
}

.main-nav a:hover,
.main-nav a:focus,
.main-nav a.active {
    color: var(--link-hover);
    border-bottom-color: var(--link-hover);
    text-decoration: none;
}

.content {
    padding: 36px 0 56px;
}

.hero {
    display: grid;
    gap: 18px;
    padding: 28px;
    border: 1px solid var(--line);
    background: var(--soft-panel);
    border-radius: 3px;
}

.hero h1 {
    font-size: clamp(2.2rem, 3vw, 4.8rem);
    line-height: 1.08;
    margin: 0;
    color: var(--text);
    font-weight: 700;
}

.lead {
    color: var(--text);
    font-size: 1.08rem;
    max-width: 860px;
    margin: 0;
}

.kicker {
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-size: 0.78rem;
    font-weight: 700;
}

.diagram {
    background: #ffffff;
    border: 1px solid var(--line);
    border-radius: 3px;
    padding: 16px;
    overflow-x: auto;
    color: var(--text);
    font-family: "Courier New", Courier, monospace;
    font-size: 0.95rem;
    line-height: 1.45;
}

.button-row {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.button {
    display: inline-block;
    background: var(--button-bg);
    color: var(--button-text);
    font-weight: 700;
    padding: 9px 14px;
    border-radius: 3px;
    border: 1px solid var(--button-bg);
    text-decoration: none;
}

.button.secondary {
    background: #ffffff;
    color: var(--link);
    border: 1px solid var(--strong-line);
}

.button:hover,
.button:focus {
    text-decoration: none;
    color: var(--button-text);
    background: var(--link-hover);
    border-color: var(--link-hover);
}

.button.secondary:hover,
.button.secondary:focus {
    color: var(--link-hover);
    background: #f3f6f8;
    border-color: var(--strong-line);
}

.section {
    margin-top: 38px;
}

.section h2 {
    border-bottom: 1px solid var(--line);
    padding-bottom: 8px;
    color: var(--text);
    font-size: 1.45rem;
}

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

.card {
    border: 1px solid var(--line);
    background: #ffffff;
    border-radius: 3px;
    padding: 20px;
}

.card h3 {
    margin-top: 0;
    color: var(--text);
}

.card p {
    color: var(--text);
}

.meta {
    color: var(--muted);
    font-size: 0.94rem;
}

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

.clean-list li {
    border-bottom: 1px solid var(--line);
    padding: 14px 0;
}

.clean-list li:last-child {
    border-bottom: 0;
}

.tag {
    display: inline-block;
    color: var(--text);
    border: 1px solid var(--line);
    background: #ffffff;
    border-radius: 3px;
    padding: 3px 8px;
    font-size: 0.86rem;
    margin: 0 6px 6px 0;
}

.site-footer {
    border-top: 1px solid var(--line);
    background: var(--soft-panel);
    color: var(--text);
    padding: 32px 0 20px;
}

.site-footer p {
    color: var(--muted);
}

.footer-grid {
    display: grid;
    grid-template-columns: 1.2fr 1fr 1fr;
    gap: 24px;
}

.copyright {
    border-top: 1px solid var(--line);
    margin-top: 24px;
    padding-top: 16px;
    font-size: 0.92rem;
    color: var(--muted);
}

@media (max-width: 820px) {
    .header-inner {
        align-items: flex-start;
        flex-direction: column;
    }

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

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

    .hero {
        padding: 20px;
    }
}