:root{
  --bg:#f5f5f7; --panel:#fff; --ink:#1d1d1f; --muted:#86868b;
  --line:#e5e5ea; --accent:#007aff; --accent-ink:#fff;
  --front:#ff9500; --back:#34c759; --warn:#ff3b30;
}
*{box-sizing:border-box;margin:0;padding:0;
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"PingFang SC",sans-serif}
body{background:var(--bg);color:var(--ink);padding:24px 16px;line-height:1.5}
.app{max-width:1040px;margin:0 auto}
header h1{font-size:24px;font-weight:600;letter-spacing:-.02em}
header .lede{color:var(--muted);font-size:14px;margin-top:6px;max-width:680px}
main{display:flex;gap:28px;flex-wrap:wrap;margin-top:24px;align-items:flex-start}

/* 左面板 */
.panel{width:380px;background:var(--panel);border:1px solid var(--line);
  border-radius:16px;padding:20px;flex:0 0 auto}
/* 上传区 */
.drop{border:1.5px dashed var(--line);border-radius:14px;background:#fafafa;
  padding:26px 16px;text-align:center;cursor:pointer;transition:.15s}
.drop:hover{border-color:var(--accent);background:#f3f8ff}
.drop.busy{opacity:.6;pointer-events:none}
.drop-plus{font-size:30px;line-height:1;color:var(--accent);font-weight:300}
.drop-main{font-size:15px;font-weight:600;margin-top:8px}
.drop-sub{font-size:12px;color:var(--muted);margin-top:4px}

/* 缩略图 + 交换 */
.thumbs{display:flex;flex-direction:column;align-items:center;gap:8px;margin-top:16px}
.thumbs[hidden]{display:none}
.thumb{position:relative;width:100%;aspect-ratio:1.585/1;border:1px solid var(--line);
  border-radius:10px;background:#fafafa;display:flex;align-items:center;justify-content:center;
  cursor:pointer;overflow:hidden;transition:.15s}
.thumb:hover{border-color:var(--accent)}
.thumb img{width:100%;height:100%;object-fit:contain}
.thumb .ph{color:var(--muted);font-size:12px}
.thumb .tag{position:absolute;top:6px;left:6px;z-index:2;background:rgba(0,0,0,.62);color:#fff;
  font-size:11px;font-weight:600;padding:2px 8px;border-radius:6px;letter-spacing:.05em}
.thumb.loading::after{content:'识别中…';position:absolute;inset:0;display:flex;
  align-items:center;justify-content:center;background:rgba(255,255,255,.82);
  font-size:13px;font-weight:600;color:var(--accent)}
.btn.swap{align-self:stretch;flex:0 0 auto}

.export-row{display:flex;gap:10px;flex-wrap:wrap;margin-top:18px}
.btn{appearance:none;border:none;background:var(--accent);color:var(--accent-ink);
  font-size:14px;font-weight:600;padding:11px 12px;border-radius:10px;cursor:pointer;
  display:inline-flex;align-items:center;justify-content:center;flex:1;min-width:96px}
.btn:hover{filter:brightness(1.05)}
.btn.ghost{background:#fff;border:1px solid var(--line);color:var(--ink)}
.btn.primary{background:var(--accent)}
.btn:disabled{opacity:.5;cursor:default}
.btn.sm{padding:8px 12px;font-size:13px;flex:0 0 auto}
.btn.tool{padding:7px 10px;font-size:12px;flex:0 0 auto;min-width:0}

.hint{font-size:12px;color:var(--muted);line-height:1.6;margin-top:14px}
.hint b{color:var(--ink)}
.toast{margin-top:12px;font-size:13px;color:var(--back);font-weight:600;min-height:18px}

/* 右侧预览 */
.preview{flex:1;min-width:320px}
.preview h2{font-size:15px;font-weight:600;margin-bottom:14px}
.scale-note{font-size:12px;color:var(--muted);font-weight:400}
.a4{width:440px;max-width:100%;border:1px solid var(--line);border-radius:12px;
  background:#fff;box-shadow:0 10px 40px rgba(0,0,0,.10);padding:14px;
  display:flex;flex-direction:column;align-items:center}
#previewCanvas{width:100%;height:auto;display:block;border-radius:8px}
.legend{display:flex;gap:18px;margin-top:14px;font-size:12px;color:var(--muted)}
.legend .dot{display:inline-block;width:10px;height:10px;border-radius:50%;margin-right:5px}
.legend .front{background:var(--front)}
.legend .back{background:var(--back)}

/* 抠图矫正模态 */
.crop-modal{position:fixed;inset:0;background:rgba(0,0,0,.78);display:flex;
  align-items:flex-start;justify-content:center;z-index:60;padding:16px;overflow-y:auto}
.crop-modal[hidden]{display:none}
.crop-box{background:#fff;border-radius:16px;max-width:min(94vw,880px);width:100%;
  padding:14px;margin:auto;max-height:92vh;overflow-y:auto}
.crop-header{display:flex;align-items:center;gap:10px;margin-bottom:10px;flex-wrap:wrap}
.crop-title{font-weight:600;font-size:15px;margin-right:auto}
.crop-tools{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:10px}
.crop-stage{position:relative;width:100%;height:min(70vh,640px);
  display:flex;align-items:center;justify-content:center;overflow:hidden;
  background:#111;border-radius:10px;touch-action:none}
#cropCanvas{max-width:100%;max-height:100%;display:block}
.corner{position:absolute;width:26px;height:26px;margin:-13px 0 0 -13px;border-radius:50%;
  background:#fff;border:3px solid #007aff;box-shadow:0 1px 6px rgba(0,0,0,.4);
  cursor:move;pointer-events:none}
.edge{position:absolute;width:16px;height:16px;margin:-8px 0 0 -8px;
  background:#fff;border:2.5px solid #34c759;transform:rotate(45deg);
  box-shadow:0 1px 6px rgba(0,0,0,.4);cursor:move;pointer-events:none}
.crop-tune{display:flex;align-items:center;gap:10px;margin-top:12px;font-size:13px;color:var(--muted)}
.crop-tune label{flex:none;white-space:nowrap}
.crop-tune input[type=range]{flex:1;min-width:0;accent-color:#0a84ff;height:28px}
.crop-tune span{flex:none;width:46px;text-align:right;font-variant-numeric:tabular-nums;color:var(--fg,#111)}
.crop-actions{display:flex;gap:10px;margin-top:10px}
.crop-hint{font-size:12px;color:var(--muted);margin-top:10px;line-height:1.5}

/* 长按保存降级弹层 */
.modal{position:fixed;inset:0;background:rgba(0,0,0,.55);display:flex;
  align-items:center;justify-content:center;z-index:50;padding:24px}
.modal[hidden]{display:none}
.modal-box{background:#fff;border-radius:16px;padding:20px;max-width:92%;text-align:center}
.modal-box img{max-width:100%;max-height:68vh;border-radius:8px;display:block;margin:0 auto}
.modal-box p{font-size:14px;margin:12px 0 14px}

@media (max-width:760px){
  main{flex-direction:column}
  .panel{width:100%}
  .a4{width:100%}
}