Two of your donut devices facing each other, hole-to-hole, with only the space between them connecting them. Each has its own two speaker tones driving a wire coil, and each has a magnet floating in ferrofluid inside. Set their tones the same for a matched pair or different for a mismatched one. Flip a device's wire polarity to make its magnet spin the other way.
Honest answer: the magnetic field you see (the glowing lines) is real, computed from the wire and the magnet by the actual physics equations. The ferrofluid is only partly in: it acts as the thick liquid the magnet pushes through, but its own magnetism — the way real ferrofluid pulls and concentrates the field — is NOT yet computed here. Adding that is a separate, heavier calculation. Ask and it can be put in as a first-order effect, clearly labeled.
They dive through each hole, balloon out past the shell, and curl back — the true shape of this kind of magnet, computed live. Where the two devices meet with opposite polarity, their fields refuse to merge and a flat "dead zone" forms in the middle, which is why opposite-wired devices push apart. Push the Power toward 6 and the lines break up, exactly as the real device did as it melted.
"Magnet speed" is how fast each magnet laps its ring. "In step" tells you if the two have locked together. "Push/pull force" is whether the devices attract or repel right now. "Tones overlap" tells you if both devices are playing the same two notes.