*{box-sizing:border-box;margin:0;padding:0;font-family:Segoe UI,sans-serif}body{background-color:#f4f6f8}.app{max-width:900px;margin:auto;padding:20px}h1{text-align:center;color:#2c3e50;margin-bottom:30px}.card{background:#fff;border-radius:10px;margin-bottom:20px;padding:20px;box-shadow:0 4px 12px #00000014}.card h3{color:#34495e;margin-bottom:15px}input,select{border:1px solid #ccc;border-radius:6px;width:100%;margin-bottom:12px;padding:10px;font-size:15px}button{color:#fff;cursor:pointer;background-color:#3498db;border:none;border-radius:6px;width:100%;padding:10px;font-size:16px}button:hover{background-color:#2980b9}ul{padding-left:0;list-style:none}li{border-bottom:1px solid #eee;padding:8px}.balance-item{margin-top:8px;font-weight:500}.receive{color:green}.owe{color:red}