Glowing points on the canvas can be dragged,
as shown in this video clip:
At every step, the red line is rotated by a small amount.
The
Try dragging the point on the canvas. Also, try changing the step-count.
Try moving the line points while the box is rolling.
This is a concrete instance of Pythagoras' theorem.
It illustrates 3² + 4²
equals 5².
Press START.
Choose the numerator and denominator. Then press START.
An animated illustration is produced that explains long-division
for those specific numbers.
YouTube animations cannot do this.
Drag the green object. See how the red image changes.
Drag F₁ to change the focal length. Bring F₁ to the left of the lens to make it concave.