.counter {
  display: inline-flex;
  overflow: hidden;
  height: 1.2em;   /* 与 JS 中的 lineHeight 一致 */
  line-height: 1.2em;
}

.digit-column {
  display: flex;
  flex-direction: column;
  will-change: transform;
}

.digit-column span {
  height: 1.2em;
  text-align: center;
  display: block;
}