*{box-sizing:border-box;font-family:system-ui,sans-serif}body{background:#f4f5f7;margin:0}.app{max-width:420px;margin:60px auto;padding:24px;background:#fff;border-radius:10px;box-shadow:0 2px 10px #00000014}h1{font-size:20px;text-align:center;margin-bottom:20px}input{display:block;width:100%;padding:10px;margin:8px 0;border:1px solid #ddd;border-radius:6px}button{padding:10px 14px;border:none;border-radius:6px;background:#4f46e5;color:#fff;cursor:pointer}button.link{background:none;color:#4f46e5;margin-top:8px}.error{color:#dc2626;font-size:14px}.header{display:flex;justify-content:space-between;align-items:center}.todo-box form{display:flex;gap:8px}.todo-box form input{flex:1}ul{list-style:none;padding:0;margin-top:16px}li{display:flex;justify-content:space-between;align-items:center;padding:8px 0;border-bottom:1px solid #eee}li span{cursor:pointer}li.done span{text-decoration:line-through;color:#999}li button{background:#ef4444;padding:4px 10px}