.stepper {
  display: flex;
  color: #333333;
}
.stepper .btn {
  width: 6.4vmin;
  height: 6.4vmin;
  background-color: #f2f3f5;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
}
.stepper .number {
  display: block;
  width: 10.6vmin;
  height: 6.4vmin;
  margin: 0 3px;
  text-align: center;
  font-weight: bold;
  font-size: 3.7vmin;
  background-color: #f2f3f5;
}
.stepper .reduce .line{
  height: 2px;
  width: 3vmin;
  background: #333333;
}
.stepper .reduce .gray{
  background: #cfcfcf;
}
.stepper .add .start-cell{
  width: 2px;
  height: 2px;
  position: relative;
}
.stepper .add .left-line {
  width: 1.4vmin;
  height: 1.4vmin;
  position: absolute;
  bottom:0;
  left: 0;
  border-left: 2px solid #333333;
  border-bottom: 2px solid #333333;
}
.stepper .add .right-line {
  width: 1.4vmin;
  height: 1.4vmin;
  position: absolute;
  top:0;
  right: 0;
  border-top: 2px solid #333333;
  border-right: 2px solid #333333;
}

.stepper .gray .left-line {
  border-left: 2px solid #cfcfcf;
  border-bottom: 2px solid #cfcfcf;
}
.stepper .gray .right-line {
  border-top: 2px solid #cfcfcf;
  border-right: 2px solid #cfcfcf;
}