:root{font-family:system-ui,-apple-system,Segoe UI,Roboto,sans-serif;color:#1a1a1a;background:#fafafa}*{box-sizing:border-box}body{margin:0}a{color:#2563eb}.app-shell{min-height:100vh;display:flex;flex-direction:column}.app-header{display:flex;gap:1rem;align-items:center;padding:.75rem 1.25rem;border-bottom:1px solid #e5e5e5;background:#fff}.app-header nav{display:flex;gap:1rem;flex-wrap:wrap}.app-header .spacer{flex:1}.app-main{flex:1;width:100%;max-width:880px;margin:0 auto;padding:1.5rem 1.25rem}.card{border:1px solid #e5e5e5;border-radius:8px;background:#fff;padding:1.25rem}.muted{color:#666}button{cursor:pointer}