*{box-sizing:border-box}body{margin:0;font:17px/1.6 Georgia,"Times New Roman",serif;color:#1d232a;background:#fbfbf8}
header,main,footer{max-width:720px;margin:0 auto;padding:1rem 1.25rem}
header{display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid #ddd;font-family:system-ui,sans-serif}
.brand{font-weight:700;color:#1d232a;text-decoration:none}nav a{margin-left:1rem}
a{color:#1f5f8b}h1{font-size:2rem;line-height:1.2}.lead{font-size:1.15rem}
.ruo-box{border-left:4px solid #1f5f8b;background:#eef3f7;padding:.75rem 1rem;font-family:system-ui,sans-serif}
.signup{border:1px solid #ddd;padding:1rem 1.25rem;background:#fff;font-family:system-ui,sans-serif}
input,button{font:inherit;padding:.5rem;margin:.25rem 0;width:100%;max-width:360px;display:block}button{background:#999;color:#fff;border:0}
footer{border-top:1px solid #ddd;font-size:.85rem;color:#555;font-family:system-ui,sans-serif}