body{font-family:Arial,sans-serif;background:#f0f0f0;padding:2rem;text-align:center}.app{max-width:600px;margin:auto;background:#fff;padding:1.5rem;border-radius:8px;box-shadow:0 2px 8px #0000001a}input[type=file]{margin-top:1rem}button{margin-top:.5rem;padding:.5rem 1rem;background:#111;color:#fff;border:none;border-radius:4px;cursor:pointer}button:disabled{background:#555;cursor:not-allowed}.tracks{margin-top:1.5rem}.track{margin-bottom:1rem}