width (1, 2, or 4 color clocks wide) Each Player/Missile object is vertically the height of the entire screen. Variable pixel height when the data is supplied by ANTIC DMA (single or double scan lines per data) Ability to independently shift each P/M object by one scan line vertically when operating on double scan lines per data. Each Player and its associated Missile has a dedicated color register separate from the Playfield colors. Multiple priority schemes for the order of graphics layers (P/M Graphics vs playfield) Color merging between Players and Playfield producing extra colors. Color merging between pairs of Players producing multi-color Players. Missiles can be grouped together into a Fifth Player that uses a separate color register. Collision detection between Players, Missiles, and Playfield graphics. There are no fixed colors for normal (CTIA) color interpretation mode. All colors are generated via indirection through nine color registers. (Four for Player/Missile graphics, four for the Playfield, and one shared between the Playfield and the Fifth Player feature.) Normal color interpretation mode provides choice of colors from a 128 color palette (16 colors with 8 luminance values for each) A GTIA color interpretation mode can generate 16 luminances per color providing a 256 color palette. The GTIA version of the chip adds three alternate color interpretation modes for the Playfield graphics. 16 shades of a single hue from the 16 possible hues in the Atari palette. This is accessible in Atari BASIC as Graphics 9. 15 hues in a single shade/luminance value plus background. This is accessible in Atari BASIC as Graphics 11. 9 colors in any hue and luminance from the palette accomplished using all the Player/Missile and Playfield color registers for the Playfield colors. This is accessible in Atari BASIC as Graphics 10. Reads the state of the joystick triggers (bottom buttons only for the Atari 5200 controllers). It includes four input/output pins that are used in different ways depending on the system: In Atari 8-bit computers, three of the pins are used to read state of the console keys (Start/Select/Option). The fourth pin controls the speaker built into the Atari 400/800 to generate keyboard clicks. On later models there is no speaker, but the key click is still generated by GTIA and mixed with the regular audio output. In the Atari 5200, the pins are used as part of the process to read the controller keyboards. Versions by