The fulcrum of the MathCats Scale was passive. Was expressing only the result of the supposed slope of the balance. It was not really interactive.

In the new Android program, Fractions Scroll, the fulcrum of MathCats is already interactive. It responds to the touch, being able to move the fractions with the finger. From left to right (swipe)

This causes the slope indicator corresponding to the chosen fraction (on the right) to be tilted,

Scrolling up and down widens or reduces the range of fractions used in the program: Increases or decreases the maximum denominator and numerator used.

Fractions Scroll Video: https://www.youtube.com/watch?v=bQbdxCfAPEc

Fractions Scroll App: https://play.google.com/store/apps/details?id=com.nummolt.slope.tap

In the paid version: "Fractions Scroll Gravity Lever" this interaction can also be obtained by tilting the device during the fifteen seconds of use of the accelerometers after pressing the corresponding button.

In this version, when the accelerometers are running, the bar that indicates the slope corresponding to the chosen fraction always remains horizontal.

Fractions Scroll Gravity Lever Video: https://www.youtube.com/watch?v=F_fH5XMlIRI

Fractions Scroll Gravity Lever App: https://play.google.com/store/apps/details?id=com.nummolt.slope.gravity

Fractions Scroll Gravity Lever: Also available at Amazon:

Blog about MathCats Balance and Fractions Balance: