:root {
    --bg: #FBFAF8;
    --surface: #F1F0EC;
    --text: #1E2124;
    --muted: #5C6066;
    --accent: #2354D6;
    --accent-dark: #17357F;
    --border: #DCDAD3;
    --radius: 10px;
    --font: system-ui, -apple-system, "Hiragino Kaku Gothic ProN",
            "Noto Sans JP", "Yu Gothic", sans-serif;
}

html {
    scroll-padding-top: 70px;
    /* 固定ヘッダーの高さ分だけ上の空きを確保 */
    scroll-behavior: smooth;
    /* ページ内スクロールを滑らかにする */
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    line-height: 1.75;
}

h1, h2, h3 {
    line-height: 1.35;
    font-weight: 700;
}

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

a:hover,
a:focus-visible {
    text-decoration: underline;
}

/* ---------- header / nav ---------- */

.site-header {
    position: sticky;
    top: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    z-index: 10;
}

.nav-wrap {
    max-width: 900px;
    margin: 0 auto;
    padding: 14px 20px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.brand {
    font-weight: 700;
    color: var(--text);
    font-size: 1.05rem;
}

.site-nav ul {
    list-style: none;
    display: flex;
    gap: 24px;
    margin: 0;
    padding: 0;
}

.site-nav a {
    color: var(--text);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    width: 32px;
    height: 32px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0;
}

.nav-toggle span {
    display: block;
    height: 2px;
    background: var(--text);
    border-radius: 2px;
}

/* ---------- hero ---------- */

.hero {
    max-width: 900px;
    margin: 0 auto;
    padding: 64px 20px 40px;
}

.hero h1 {
    font-size: clamp(1.8rem, 4vw, 2.6rem);
    margin: 0 0 16px;
}

.hero .lead {
    max-width: 60ch;
    color: var(--muted);
    font-size: 1.05rem;
    margin: 0 0 20px;
}

.badge {
    display: inline-block;
    background: var(--accent);
    color: #fff;
    padding: 6px 16px;
    border-radius: 999px;
    font-size: 0.9rem;
}

/* ---------- content grid ---------- */

.content-grid {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px 20px 60px;
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 32px;
    align-items: start;
}

.content-grid h2 {
    font-size: 1.4rem;
}

.content-grid h3 {
    font-size: 1.1rem;
    margin-top: 32px;
}

.tip {
    background: var(--surface);
    border-left: 4px solid var(--accent);
    border-radius: var(--radius);
    padding: 20px 24px;
}

.tip h3 {
    margin-top: 0;
    font-size: 1rem;
}

.tip ul {
    margin: 0;
    padding-left: 20px;
}

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

/* ---------- about ---------- */

.about {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 20px 60px;
    border-top: 1px solid var(--border);
    padding-top: 40px;
}

/* ---------- footer ---------- */

.site-footer {
    border-top: 1px solid var(--border);
    padding: 24px 20px;
    text-align: center;
    color: var(--muted);
    font-size: 0.9rem;
}

/* ---------- responsive ---------- */

@media (max-width: 700px) {
    .nav-toggle {
        display: flex;
    }

    .site-nav {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--bg);
        border-bottom: 1px solid var(--border);
        display: none;
    }

    .site-nav.open {
        display: block;
    }

    .site-nav ul {
        flex-direction: column;
        gap: 0;
        padding: 8px 20px 16px;
    }

    .site-nav li {
        padding: 10px 0;
        border-bottom: 1px solid var(--border);
    }

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