:root{color-scheme:light dark;font-family:system-ui,sans-serif}body{margin:0}.app{max-width:960px;margin:0 auto;padding:16px}header{display:flex;justify-content:space-between;align-items:center;gap:8px}.cols{display:grid;grid-template-columns:240px 1fr;gap:16px}@media(max-width:640px){.cols{grid-template-columns:1fr}}ul{list-style:none;padding:0;margin:8px 0}li{display:flex;gap:8px;align-items:center;padding:4px 0}li.sel{font-weight:600}input{padding:6px 8px}button{padding:6px 10px;cursor:pointer}.err{color:#c00}