.tab {
    display: none;
  }
  .step {
    height: 15px;
    width: 15px;
    margin: 0 2px;
    background-color: #bbbbbb;
    border: none;  
    border-radius: 50%;
    display: inline-block;
    opacity: 0.5;
  }

  .step.active {
    opacity: 1;
  }

/* Mark the steps that are finished and valid: */
.step.finish {
    background-color: #4CAF50;
  }
  /* Mark input boxes that gets an error on validation: */
input.invalid {
    background-color: #ffdddd;
  }