* {
    box-sizing: border-box;
}


body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    margin: 0;
    padding: 0;
}

/* ── Centered layout wrapper ─────────────────────────────── */

.layout {
    display: flex;
    max-width: 1080px;
    margin: 0 auto;
    min-height: 100vh;
}

/* ── Sidebar ─────────────────────────────────────────────── */

header {
    position: sticky;
    top: 0;
    align-self: flex-start;
    width: 220px;
    flex-shrink: 0;
    height: 100vh;
    overflow-y: auto;
    padding: 30px 20px;
    border-right: 1px solid #efefef;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

header h1 {
    margin: 0;
    font-size: 1.1rem;
}

header h1 a {
    color: #333;
    text-decoration: none;
}

.header-logo {
    max-width: 100%;
    display: block;
    margin-bottom: 6px;
}

.blog-description {
    margin: 0;
    color: #666;
    font-size: 0.85em;
}

.main-nav {
    margin-top: 10px;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.nav-item {
    display: block;
    padding: 6px 10px;
    border: 1px solid #efefef;
    border-radius: 8px;
    color: #333;
    text-decoration: none;
    font-size: 0.9em;
    font-weight: 600;
    transition: all 0.2s ease;
}

.nav-item:hover {
    background-color: #f5f5f5;
    border-color: #0066cc;
    color: #0066cc;
}

/* ── Main content ─────────────────────────────────────────── */

.page-body {
    flex: 1;
    min-height: 100vh;
    overflow-y: auto;
    padding: 40px 40px 60px;
    max-width: 860px;
}

img {
    max-width: 100%;
}

hr {
    border: 1px solid #efefef;
}

a {
    color: #0066cc;
    text-decoration: none;
    font-size: 0.95em;
}

.post {
    padding: 15px;
    margin-top: 10px;
    border: 1px solid #efefef;
    border-radius: 10px;
}

.post-meta {
    color: #666;
    font-size: 0.9em;
    margin-bottom: 10px;
}

.post-title {
    margin: 10px 0;
}

.post-title a {
    color: #333;
    text-decoration: none;
}

.post-title a:hover {
    color: #0066cc;
}

footer {
    margin-top: 60px;
    padding-top: 20px;
    border-top: 1px solid #efefef;
    text-align: center;
    color: #666;
    font-size: 0.9em;
}

footer p {
    font-size: 0.7rem;
}

pre {
    background-color: #f1f1f1;
    padding: 10px;
    border: 1px solid #efefef;
    white-space: pre-wrap;
}

/* ── Mobile ───────────────────────────────────────────────── */

@media (max-width: 640px) {
    .layout {
        flex-direction: column;
    }

    header {
        position: static;
        top: auto;
        left: auto;
        width: 100%;
        height: auto;
        overflow-y: visible;
        border-right: none;
        border-bottom: 1px solid #efefef;
        padding: 20px;
        flex-direction: column;
        align-items: flex-start;
        flex-wrap: nowrap;
        gap: 4px;
    }

    header h1 {
        flex: 1 1 100%;
    }

    .blog-description {
        flex: 1 1 100%;
    }

    .main-nav {
        flex-direction: row;
        flex-wrap: wrap;
        margin-top: 4px;
    }

    .page-body {
        margin-left: 0;
        padding: 20px;
    }
}