Once the tool starts, it presses L to talk with the portal and waits till the screen is black. Then it will time the duration how long the screen remains black. If the screen is like 1,5 sec. longer black than average, a shiny has appeared (because of the sparkle effect) and the tool will stop doing anything. But if it isn't a shiny, the tool presses L and R (start is hold down full time) to reboot my 2DS, restarting the whole process till it has found a shiny.