*{margin:0;padding:0;box-sizing:border-box;}
html{scroll-behavior:smooth;font-size:16px;}
body{
    font-family:-apple-system,BlinkMacSystemFont,"Hiragino Sans","Meiryo",sans-serif;
    color:#333;
    background:#fff;
    line-height:1.75;
}
ul,ol{list-style:none;}
a{text-decoration:none;color:inherit;}
img{max-width:100%;height:auto;display:block;loading:lazy;}
.container{width:94%;max-width:1200px;margin:0 auto;}

/* ヘッダーナビ */
header{
    background:#fff;
    box-shadow:0 2px 8px rgba(0,0,0,0.06);
    position:sticky;
    top:0;
    z-index:99;
}
.nav-wrap{
    display:flex;
    justify-content:space-between;
    align-items:center;
    height:64px;
}
.logo{font-size:22px;font-weight:bold;color:#1677ff;}
.nav-list{display:flex;gap:32px;}
.nav-list a{
    font-size:16px;
    color:#555;
    transition:color 0.2s;
}
.nav-list a:hover{color:#1677ff;}

/* トップバナー 巨大DLボタン配置 */
.banner{
    padding:80px 0;
    background:#f5f7fa;
    text-align:center;
}
.banner h1{
    font-size:42px;
    margin-bottom:20px;
    color:#1a1a1a;
}
.banner p{
    font-size:18px;
    color:#666;
    max-width:720px;
    margin:0 auto 40px;
}
.download-main-btn{
    display:inline-block;
    width:340px;
    height:72px;
    line-height:72px;
    background:#1677ff;
    color:#fff;
    font-size:22px;
    font-weight:bold;
    border-radius:10px;
    transition:all 0.25s ease;
}
.download-main-btn:hover{
    background:#0958d9;
    transform:scale(1.03);
    box-shadow:0 6px 18px rgba(22,119,255,0.3);
}

/* 汎用セクション */
.section{padding:70px 0;}
.section-title{
    font-size:30px;
    text-align:center;
    margin-bottom:50px;
}
.card-row{
    display:grid;
    grid-template-columns:repeat(auto-fit,minmax(280px,1fr));
    gap:30px;
}
.card{
    background:#f5f7fa;
    padding:30px;
    border-radius:12px;
}
.card h3{font-size:20px;margin-bottom:12px;color:#1a1a1a;}
.card p{color:#666;}

/* ダウンロードページ OS別ボタン */
.platform-btn{
    display:block;
    width:100%;
    max-width:420px;
    margin:16px auto;
    padding:18px;
    background:#1677ff;
    color:#fff;
    text-align:center;
    font-size:18px;
    border-radius:8px;
}
.platform-btn.mac{background:#222;}
.platform-btn:hover{opacity:0.92;}

/* 解説ページ手順ブロック */
.step-item{
    margin-bottom:24px;
    padding:24px;
    background:#f5f7fa;
    border-left:5px solid #1677ff;
    border-radius:0 8px 8px 0;
}
.step-item h4{font-size:20px;margin-bottom:8px;}

/* フッター */
footer{
    background:#1a1a1a;
    color:#aaa;
    padding:50px 0 30px;
    margin-top:40px;
}
.footer-nav{
    display:flex;
    gap:24px;
    justify-content:center;
    margin-bottom:30px;
}
.footer-nav a{color:#ddd;}
.copyright{text-align:center;font-size:14px;}

/* スマホ対応 */
@media screen and (max-width:768px){
    .banner h1{font-size:28px;}
    .download-main-btn{width:90%;font-size:18px;height:60px;line-height:60px;}
    .nav-list{gap:16px;}
    .nav-wrap{height:auto;padding:16px 0;flex-direction:column;gap:12px;}
}