The primary playfield/star field is drawn in the graphics mode that provides 160×96 bitmapped pixels utilizing four color registers at a time out of a palette of 128 colors provided by the CTIA chip in the early Atari computers. This is called ANTIC mode D, but accessed in Atari BASIC by use of the "GRAPHICS 7" command. The Atari's use of an indirect palette means that color changes associated with the presence or absence of energy shields, emergency alarms, and the screen flash representing destruction of the ship can be accomplished by simply changing the palette values in memory registers.