So far there are eight demos:
Adding Sines (and other waveforms). Demonstrates what happens when you add sine waves, triangle waves and square waves.
Phase and Frequency. Demonstrates the relationship between period, angle, phase and frequency. Also shows how a real oscillation can be produced by two complex oscillations.
Phasors. Demonstrates the relationship between a phasor and the real oscillation that it represents.
Adding Phasors. Demonstrates the relationship between a phasor and the real oscillation that it represents.
Fields and Flux. Demonstrates the relationship between fields strength and flux, and the field patterns around charges, dipoles and charged plates.
The Drude Model. Demonstrates the motion of electrons in a conductor according to the Drude model (and some other assumptions).
Electrons in Solids. Demonstrates the motion of electrons in the conduction and valence bands of insulators, conductors and semiconductors, and a simplified version of the pn-junction.
The Bode Approximation. Allows you to place poles and zeros, and plot the amplitude and phase response, together with the Bode approximations.
Online Oscilloscope. This one allows you to play around with the typical controls that an oscilloscope provides. It also has the capability to use a Nucleo board (STM32L476) as a real analogue input and output.