code: private void updateReversing(double extrp)
      {
          current -= speed * extrp;
  
          // First frame reached, done
          if (Double.compare(current, first) <= 0)
          {
              current = first;
  
              if (repeat)
              {
                  state = AnimState.PLAYING;
                  current += 1.0;
              }
              else
              {
                  state = AnimState.FINISHED;
              }
          }
      }
docs: Update in reverse mode routine.
  
  @param extrp The extrapolation value.