Select Numerators and Denominators. Look at visualization of the fractions. Note: Numerator cannot be larger then Denominator. Fraction A + Fraction B = Red + Green dots / total dots Visualizes adding fractions after giving them a common Denominator.
Credit to @crkcity for the source project. I just changed the visualization from solid, colored rectangles (with transparencies) to co-existing dots. To simplify the graphics, I limited the Numerator to be no more than the Denominator (N <= D). To do that, I used custom "sliders", so that I had on-the-fly control over the slider ranges.
