As with many instructables, that one has some serious deficiencies:
-
2N3904 or BC548 would be very poor choices for the transistor, especially if you want to scale it to more LEDs. 2N2222A or BC337 would be OK.
-
22K is far too large a value for the base resistor. 1K would be a better value to use, or 220 ohms for larger cubes.