This is a collection of tools for experimenting with physics and building intuition.
My favorite demonstration of this tool involves the relativistic Doppler effect. The red person starts at (0, 0) and moves with a velocity of 0. The blue person starts at (0, 0) and moves with a velocity of 0.6c. The red person emits a pulse of light every second, so light pulses start at (ct, x) = (n, 0), where n is a positive integer, and they move with a velocity of 1c.
If we transform to a different frame of reference where the blue person is at rest, it becomes clear that the blue person receives a pulse of light every 2 seconds. This is consistent with the theoretical result:
Visualization for Electric Field and Potential