:root{--primary: #3f40d1;--bg: #ffffff}*{box-sizing:border-box}body{margin:0;font-family:Inter,sans-serif;background:#f9f9f9;color:#333}.app{min-height:100vh;display:flex;align-items:center;justify-content:center;padding:24px}.card{width:760px;max-width:95%;background:#fff;border-radius:12px;box-shadow:0 6px 30px #0000001a;padding:32px;border:1px solid rgba(0,0,0,.08)}h1{color:#3f40d1;margin:0 0 8px;font-size:24px;text-align:center}.quality-info{margin-bottom:16px}.subtitle{font-size:14px;color:#666;margin:0;text-align:center;font-weight:500}input[type=file]{display:none}.file-input-wrapper{display:flex;flex-direction:column;align-items:center;gap:12px;margin-bottom:16px}.file-input-button{background:var(--primary);color:#fff;border:none;padding:12px 20px;border-radius:8px;cursor:pointer;font-size:16px;transition:background .3s ease,transform .2s ease}.file-input-button:hover{background:#2e2fc4;transform:scale(1.05)}.file-name{font-size:14px;color:#333}.btn{background:#3f40d1;color:#fff;border:none;padding:12px 20px;border-radius:8px;cursor:pointer;font-size:16px;transition:background .3s ease,transform .2s ease;display:block;margin:8px auto}.btn:hover{background:#2e2fc4;transform:scale(1.05)}.status{margin-top:12px;font-size:14px;text-align:center;color:#555}.processing{margin-top:8px;font-size:14px;color:#ff9800;text-align:center}.result{margin-top:24px;text-align:center}.download{display:inline-block;margin-top:12px;color:#3f40d1;font-weight:600;text-decoration:none;transition:color .3s ease}.download:hover{color:#2e2fc4}.preview-frame{width:100%;height:600px;border:1px solid #eee;margin-top:12px}.header{display:flex;flex-direction:column;align-items:center;margin-bottom:16px}.back-button{background:#f44336;color:#fff;border:none;padding:12px 20px;border-radius:8px;cursor:pointer;font-size:16px;transition:background .3s ease,transform .2s ease;margin:0;position:relative;top:-10px;left:0}.back-button:hover{background:#d32f2f;transform:scale(1.05)}.title{text-align:center;margin-top:8px}