:root {
    --primary-color: #333;
    --secondary-color: #666;
    --background-color: #f4f4f4;
    --card-background: #fff;
    --border-color: #e0e0e0;
    --accent-color: #007bff;
    --font-family: "Helvetica Neue", Arial, "Hiragino Kaku Gothic ProN", "Hiragino Sans", Meiryo, sans-serif;
}

body {
    font-family: var(--font-family);
    line-height: 1.6;
    margin: 0;
    background-color: var(--background-color);
    color: var(--primary-color);
}

a {
    text-decoration: none;
    color: inherit;
    transition: opacity 0.3s;
}

a:hover {
    opacity: 0.8;
}

main {
    max-width: 960px;
    margin: 0 auto;
    padding: 40px 20px;
    min-height: calc(100vh - 150px);
}

/* ヘッダー */
.site-header {
    background-color: var(--card-background);
    border-bottom: 1px solid var(--border-color);
    padding: 10px 20px;
    position: sticky; /* 追従させると利便性アップ */
    top: 0;
    z-index: 1000;
}

.header-inner {
    max-width: 960px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.site-logo {
    font-size: 24px;
    font-weight: bold;
    margin: 0;
}

/* ナビゲーション - デフォルト(PC) */
.main-nav ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    gap: 20px;
}

.main-nav a {
    font-size: 14px;
    font-weight: 500;
}

/* 広告スペースの修正 */
.ad-space {
    margin: 30px 0;
    text-align: center;
}

.ad-placeholder {
    width: 100%;
    min-height: 250px; /* 固定ではなく最小高さに */
    background-color: #f9f9f9;
    border: 1px dashed var(--border-color);
    display: flex;
    flex-direction: column; /* PR文字と画像を縦に並べる */
    align-items: center;
    justify-content: center;
    color: var(--secondary-color);
    overflow: hidden;
}

/* コンテンツボタン */
.button-group {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.content-button {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 80px;
    padding: 15px;
    background-color: var(--card-background);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-weight: bold;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

/* フッター */
.site-footer {
    background-color: var(--primary-color);
    color: #fff;
    padding: 40px 20px;
    text-align: center;
}

/* モバイルメニュー (スマホ専用) */
@media (max-width: 767px) {
    .hamburger-menu {
        display: block;
        background: none;
        border: none;
        cursor: pointer;
        width: 30px;
        height: 24px;
        position: relative;
        z-index: 1100;
    }

    .hamburger-menu span {
        display: block;
        width: 100%;
        height: 2px;
        background-color: var(--primary-color);
        position: absolute;
        transition: 0.3s;
    }

    .hamburger-menu span:nth-child(1) { top: 0; }
    .hamburger-menu span:nth-child(2) { top: 11px; }
    .hamburger-menu span:nth-child(3) { bottom: 0; }

    /* 開いた時のアニメーション */
    .hamburger-menu[aria-expanded="true"] span:nth-child(1) { transform: translateY(11px) rotate(45deg); }
    .hamburger-menu[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
    .hamburger-menu[aria-expanded="true"] span:nth-child(3) { transform: translateY(-11px) rotate(-45deg); }

    .main-nav {
        position: fixed;
        top: 0;
        right: -100%; /* 初期は画面の外 */
        width: 100%;
        height: 100vh;
        background-color: rgba(255,255,255,0.95);
        padding-top: 80px;
        transition: right 0.4s ease-in-out;
        z-index: 1050;
        display: block !important; /* display:noneを上書き */
    }

    .main-nav[aria-hidden="false"] {
        right: 0;
    }

    .main-nav ul {
        flex-direction: column;
        align-items: center;
        gap: 30px;
    }
    
    .main-nav a {
        font-size: 18px;
    }
}