A polyrhythm is two evenly-spaced pulse trains laid over the same span of time. In 3 against 2, one voice splits the beat into three, the other into two. They only strike together at the very start — the downbeat — then weave apart and snap back a beat later.
How long the woven pattern runs before it repeats is the least common multiple of the two counts. Three and two share an LCM of six; five and four share twenty. The bigger that number, the longer the ear waits for the two voices to line up — which is why 5-against-4 feels restless and slippery, and 3-against-2 feels taut and singable.
When the two counts share a factor, they lock up sooner (4-against-2 repeats every 4). Coprime counts — no shared factor — stretch the pattern out to its full length.
Drag the right wheel to slide voice B out of phase and watch the downbeat scatter; tap a wheel to mute it and hear one voice alone. Press Lock to slam them back onto a shared downbeat.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.