The L7 graffiti demo swaps out the default character set with a custom one which is used for the background graphics. The movement of the sprites on the left and right sides are controlled by a sine wave table. The other sprites like the trashcan and the speaker move when certain bits are set in the third control register SID chip $d412, making them appear to move with the music. Lastly there is a color scroller on the text giving it a wave effect.

• CBM Studio source code.
• L7 code chirping on my SX-64, seem's to like it.