Connect the longer, positive legs of (anodes) 12 LEDs to digital pins 2-13 through 220 ohm current limiting resistors. Connect the shorter, negative legs (cathodes) to ground. moves through each of the LEDS one by one, from the lowest pin to the highest. Before this loop is allowed to move from one pin to the next, two things must be accomplished.
First, you brighten the individual LED through these lines of code: