* { box-sizing: border-box; }
body {
  font-family: "Microsoft YaHei", "PingFang SC", Arial, sans-serif;
  background: #f5f6f8;
  margin: 0;
  padding: 24px;
  color: #222;
}
.container {
  max-width: 720px;
  margin: 0 auto;
  background: #fff;
  border-radius: 10px;
  padding: 28px 32px;
  box-shadow: 0 2px 10px rgba(0,0,0,0.06);
}
h1 { font-size: 20px; margin-top: 0; }
.tip {
  font-size: 13px;
  color: #666;
  background: #f0f4ff;
  border-left: 3px solid #5b7fff;
  padding: 10px 14px;
  border-radius: 6px;
  line-height: 1.6;
}
.dropzone {
  margin: 20px 0;
  border: 2px dashed #c4cbd6;
  border-radius: 10px;
  padding: 36px;
  text-align: center;
  cursor: pointer;
  position: relative;
  transition: border-color .2s, background .2s;
}
.dropzone:hover, .dropzone.dragover {
  border-color: #5b7fff;
  background: #f7f9ff;
}
.dropzone input[type="file"] {
  position: absolute;
  inset: 0;
  opacity: 0;
  cursor: pointer;
}
.dropzone p { margin: 0; color: #555; font-size: 14px; }
.options {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin: 18px 0;
  font-size: 13px;
  color: #444;
}
.options input[type="number"] {
  width: 70px;
  margin-left: 8px;
  padding: 4px 6px;
}
.fallback-label {
  font-size: 12px;
  color: #888;
}
#convertBtn {
  width: 100%;
  padding: 12px;
  background: #5b7fff;
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 15px;
  cursor: pointer;
  transition: background .2s;
}
#convertBtn:disabled {
  background: #c4cbd6;
  cursor: not-allowed;
}
#convertBtn:not(:disabled):hover { background: #4566db; }
#log {
  margin-top: 18px;
  font-size: 13px;
  color: #555;
  white-space: pre-wrap;
  line-height: 1.7;
  max-height: 240px;
  overflow-y: auto;
}
#log .err { color: #d33; }
#log .ok { color: #1a8a3e; }