Slightly off topic: Back in the early days of the Newton, there was an app that let you manipulate algebraic expressions by dragging and dropping individual el

Slightly off topic: Back in the early days of the Newton, there was an app that let you manipulate algebraic expressions by dragging and dropping individual elements of the expression. Think factoring out a common factor represented by the expression sprouting parentheses with the factor out front. There was a later effort called MathDrag'n but that seemed to run out of steam. Does anyone know if a similar thing exists and is maintained now?