The same Bloch engine the game runs on, with the lid off. Fire pulses by hand or run a named experiment, and change the sample underneath it while it goes.
A 90° tips z into the plane; a 180° inverts z and mirrors the phase fan. Each 90° starts a fresh acquisition and its FID is added to the ones before it.
These schedule the pulses for you at sensible delays, so you can watch the shape of each one rather than fight the timing.
T2 sets how fast the packets themselves die. T1 sets how fast Mz comes back, which is what limits how often you can usefully pulse.
Raise the shim and the packets fan apart: the signal dies at T2* long before T2, and the line goes broad. A 180° pulse undoes exactly this part and nothing else — which is the whole point of an echo.
1:25 means one second of your time is 40 ms of the sample's. Slow it further to watch a single packet precess.