A simulated feed hands the grid fifty instruments, then keeps resending four of them a tick with a new price. Each resend names an id already on screen, so the grid patches that row's cells rather than adding a new one, and the changed cells flash. The source is capped to forty rows, so the ones not currently ticking make way for the ones that are. Click Stop and no further updates are applied until you press Start again. Read the full how-to on latticegrid.dev.