body { font-family: Arial; margin:0; padding:0; background:white; color:#111; }
header { background:#b30000; color:white; text-align:center; padding:20px; }
.rechner { padding:20px; max-width:600px; margin:20px auto; border:1px solid #ccc; border-radius:8px; background:#fff3f3; }
form input, form select, form button {
    width:100%; padding:12px; margin:10px 0; border-radius:5px; border:1px solid #bbb;
}
form button { background:#b30000; color:white; font-weight:bold; cursor:pointer; }
form button:hover { background:#990000; }
footer { background:#eee; padding:20px; text-align:center; font-size:14px; color:#555; }