:root{font-family:system-ui,sans-serif;line-height:1.4}body{margin:0;padding:2rem;max-width:640px;margin-inline:auto}label{display:block;margin:.75rem 0 .25rem;font-weight:600}input,textarea{width:100%;padding:.5rem;box-sizing:border-box}button{padding:.6rem 1rem;cursor:pointer}.err{color:#b00020}.ok{color:#006400}