:root {
    --color-primary: #0969da;
    --color-primary-hover: #0550ae;
    --color-text: #1f2328;
    --color-text-secondary: #656d76;
    --color-border: #d0d7de;
    --color-bg: #f5f5f5;
    --color-bg-secondary: #f6f8fa;
    --color-bg-tertiary: #eaeef2;
    --color-accent-blue: #ddf4ff;
    --color-accent-green: #dafbe1;
    --color-accent-purple: #fbefff;
    --color-accent-orange: #fff1e5;
    --color-icon-blue: #0969da;
    --color-icon-green: #1a7f37;
    --color-icon-purple: #8250df;
    --color-icon-orange: #bc4c00;
    --header-height: 53px;
    --sidebar-width: 280px;
    --content-max-width: 1280px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Noto Sans JP', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text);
    background: var(--color-bg);
}

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

a:hover {
    text-decoration: underline;
}

/* ヘッダー */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--color-bg);
    /* ヘッダーの背景色 */
    border-bottom: 1px solid var(--color-border);
    z-index: 100;
    display: flex;
    align-items: center;
    padding: 0 24px;
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    max-width: var(--content-max-width);
    margin: 0 auto;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 16px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 18px;
    font-weight: 600;
    color: var(--color-text);
    margin: .2rem;
    padding: .4rem;
}

.logo:hover {
    text-decoration: none;
}

.version-badge {
    font-size: 12px;
    padding: 2px 8px;
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: 20px;
    color: var(--color-text-secondary);
    font-weight: 500;
}

/* ヘッダーナビ */
.header-nav {
    display: flex;
    align-items: center;
    gap: 8px;
}

.header-nav-link {
    padding: 8px 12px;
    font-size: 14px;
    color: var(--color-text);
    border-radius: 6px;
    transition: background 0.2s;
}

.header-nav-link:hover {
    background: var(--color-bg-secondary);
    text-decoration: none;
}

/* メインコンテンツ */
.main {
    margin-top: var(--header-height);
    min-height: calc(100vh - var(--header-height));
}

/* ヒーローセクション */
.hero {
    background: linear-gradient(180deg, var(--color-bg-secondary) 0%, var(--color-bg) 100%);
    padding: 64px 24px;
    text-align: center;
    border-bottom: 1px solid var(--color-border);
}

.hero-inner {
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: 40px;
    font-weight: 700;
    margin-bottom: 16px;
    color: var(--color-text);
}

.hero-description {
    font-size: 20px;
    color: var(--color-text-secondary);
    margin-bottom: 32px;
}

/* カテゴリセクション */
.categories {
    padding: 48px 24px;
    max-width: var(--content-max-width);
    margin: 0 auto;
}

.section-title {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 24px;
    color: var(--color-text);
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 24px;
}

.category-card {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: 24px;
    transition: all 0.2s;
    display: block;
}

.category-card:hover {
    border-color: var(--color-primary);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
    text-decoration: none;
}

.category-icon {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 16px;
}

.category-icon svg {
    width: 24px;
    height: 24px;
}

.category-icon.blue {
    background: var(--color-accent-blue);
    color: var(--color-icon-blue);
}

.category-icon.green {
    background: var(--color-accent-green);
    color: var(--color-icon-green);
}

.category-icon.purple {
    background: var(--color-accent-purple);
    color: var(--color-icon-purple);
}

.category-icon.orange {
    background: var(--color-accent-orange);
    color: var(--color-icon-orange);
}

.category-title {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--color-text);
}

.category-description {
    font-size: 14px;
    color: var(--color-text-secondary);
    line-height: 1.5;
}

/* クイックリンク */
.quick-links {
    padding: 48px 24px;
    background: var(--color-bg-secondary);
    border-top: 1px solid var(--color-border);
}

.quick-links-inner {
    max-width: var(--content-max-width);
    margin: 0 auto;
}

.quick-links-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 16px;
}

.quick-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px;
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    transition: all 0.2s;
}

.quick-link:hover {
    border-color: var(--color-primary);
    text-decoration: none;
}

.quick-link-icon {
    width: 20px;
    height: 20px;
    color: var(--color-text-secondary);
    flex-shrink: 0;
}

.quick-link-text {
    font-size: 14px;
    font-weight: 500;
    color: var(--color-text);
}

.quick-link-arrow {
    width: 16px;
    height: 16px;
    color: var(--color-text-secondary);
    margin-left: auto;
}

/* 人気のトピック */
.popular-topics {
    padding: 48px 24px;
    max-width: var(--content-max-width);
    margin: 0 auto;
}

.topics-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 16px;
}

.topic-item {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    padding: 16px;
    border-radius: 8px;
    transition: background 0.2s;
}

.topic-item:hover {
    background: var(--color-bg-secondary);
    text-decoration: none;
}

.topic-bullet {
    width: 8px;
    height: 8px;
    background: var(--color-primary);
    border-radius: 50%;
    margin-top: 8px;
    flex-shrink: 0;
}

.topic-content {
    flex: 1;
}

.topic-title {
    font-size: 15px;
    font-weight: 500;
    color: var(--color-primary);
    margin-bottom: 4px;
}

.topic-description {
    font-size: 13px;
    color: var(--color-text-secondary);
}

/* フッター */
.footer {
    background: var(--color-bg-secondary);
    border-top: 1px solid var(--color-border);
    padding: 48px 24px;
}

.footer-inner {
    max-width: var(--content-max-width);
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    flex-wrap: wrap;
    gap: 32px;
}

.footer-section {
    min-width: 160px;
}

.footer-title {
    font-size: 14px;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 16px;
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: 8px;
}

.footer-links a {
    font-size: 14px;
    color: var(--color-text-secondary);
}

.footer-links a:hover {
    color: var(--color-primary);
}

.footer-bottom {
    max-width: var(--content-max-width);
    margin: 32px auto 0;
    padding-top: 24px;
    border-top: 1px solid var(--color-border);
    text-align: center;
}

.footer-copyright {
    font-size: 13px;
    color: var(--color-text-secondary);
}

/* レスポンシブ */
@media (max-width: 768px) {
    .header {
        padding: 0 16px;
    }

    .hero {
        padding: 40px 16px;
    }

    .hero-title {
        font-size: 28px;
    }

    .hero-description {
        font-size: 16px;
    }

    .categories,
    .quick-links-inner,
    .popular-topics {
        padding: 32px 16px;
    }

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

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

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

    .footer-inner {
        flex-direction: column;
    }
}

/* モバイルメニューボタン */
.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    padding: 8px;
    cursor: pointer;
    color: var(--color-text);
}

@media (max-width: 768px) {
    .mobile-menu-btn {
        display: flex;
    }

    .header-nav {
        display: none;
    }
}