:root{color-scheme:light;font-family:Inter,system-ui,sans-serif;background:#f4f5fb;color:#1f2937}body{margin:0;min-height:100vh;background:#f4f5fb}.app-shell{max-width:760px;margin:0 auto;padding:2rem}header h1{font-size:2.5rem;margin:0}header p{margin:.5rem 0 1.75rem;color:#4b5563}.todo-form{display:flex;gap:.75rem;margin-bottom:1.5rem;margin-top:1.5rem}.todo-form input{flex:1;padding:.9rem 1rem;border:1px solid #d1d5db;border-radius:.75rem;font-size:1rem}.todo-form button{padding:.9rem 1.25rem;border:none;border-radius:.75rem;background:#2563eb;color:#fff;font-size:1rem;cursor:pointer}.todo-list{list-style:none;padding:0;margin:0}.todo-list li{display:flex;align-items:center;justify-content:space-between;background:#fff;padding:1rem;border-radius:.85rem;border:1px solid #e5e7eb;margin-bottom:.75rem}.todo-list li.completed span{text-decoration:line-through;color:#6b7280}.todo-list label{display:flex;align-items:center;gap:.75rem}.todo-list input[type=checkbox]{width:1.15rem;height:1.15rem}.delete-button{border:none;background:transparent;color:#ef4444;cursor:pointer;font-weight:600}.error{color:#b91c1c;margin-bottom:1rem}