:root{
  --bg:#f8f9fb;--fg:#0f172a;--muted:#6b7280;--brand:#111827;
  --card:#ffffff;--btn:#111827;--btn-fg:#ffffff;--safe:12px;
}
*{box-sizing:border-box;}
html,body{height:100%;}
body{margin:0;font-family:-apple-system, BlinkMacSystemFont, 'SF Pro Text','Segoe UI', Roboto, 'PingFang SC','Hiragino Sans GB','Helvetica Neue', Arial, 'Noto Sans CJK SC', sans-serif;color:var(--fg);background:var(--bg);} 
.app{max-width:680px;margin:0 auto;padding:16px;height:100%;display:flex;flex-direction:column;}
header{padding:8px 0;}
h1{font-size:28px;line-height:1.2;margin:12px 0 6px;}
h2{font-size:18px;font-weight:500;color:var(--muted);margin:0 0 16px;}
.card{background:var(--card);border-radius:16px;box-shadow:0 1px 4px rgba(0,0,0,.06);padding:20px;}
.center{display:flex;flex-direction:column;align-items:center;justify-content:center;}
.big-btn{width:100%;padding:16px 20px;border-radius:12px;border:none;background:var(--btn);color:var(--btn-fg);font-size:18px;font-weight:700;cursor:pointer;}
.big-btn:active{opacity:.9;}
.muted{color:var(--muted);font-size:12px;margin-top:10px;text-align:center;}
.progress{font-size:14px;color:#64748b;margin-bottom:12px;}
.options{display:grid;grid-template-columns:1fr;gap:12px;margin-top:12px;}
.opt{padding:14px 16px;border-radius:12px;border:1px solid #e5e7eb;background:#fff;cursor:pointer;text-align:left;font-size:16px;}
.opt:active{transform:scale(.99);}    
.row{display:flex;gap:12px;align-items:center;}
.row .big-btn{flex:1;}
.hidden{display:none;}
.result-title{font-size:22px;font-weight:800;margin-bottom:6px;}
.result-desc{font-size:15px;color:#374151;line-height:1.6;white-space:pre-line;}
.preview{width:100%;aspect-ratio:9/16;background:#eee;border-radius:12px;overflow:hidden;margin-top:12px;border:1px solid #e5e7eb;}
.preview img{width:100%;height:100%;object-fit:cover;display:block;}
.topbar{display:flex;justify-content:space-between;align-items:center;margin-bottom:8px;}
.topbar .link{font-size:14px;color:#334155;cursor:pointer;}
.spinner{position:fixed;inset:0;background:rgba(255,255,255,.8);backdrop-filter:saturate(140%) blur(4px);display:none;align-items:center;justify-content:center;z-index:40;}
.spinner.show{display:flex;}
.lds{width:60px;height:60px;border-radius:50%;border:6px solid #cbd5e1;border-top-color:#020617;animation:spin 1s linear infinite;}
@keyframes spin{to{transform:rotate(360deg)}}
.toast{position:fixed;left:50%;bottom:36px;transform:translateX(-50%);background:#111827;color:#fff;padding:10px 14px;border-radius:999px;font-size:13px;display:none;z-index:50;}
.toast.show{display:block;}
footer{margin:14px 0 8px;color:#6b7280;font-size:12px;text-align:center;}