on the bottom. When the Missiles are switched to act as a fifth Player then where the Missile objects overlap the Playfield the Missile pixels luminance merges with the Playfield pixels' Luminance value. 9 Color Unlike the other two special GTIA modes, this mode is entirely driven by color indirection. All nine color registers work on the display for pixel values 0 through 8. The remaining 7 pixel values repeat previous color registers. The pixels are delayed by one color clock (half a GTIA mode pixel) when output. This offset permits interesting effects. For an example, page flipping rapidly between this mode and a different GTIA mode produces a display with apparent higher resolution and greater number of colors. This mode is unique in that is uses color register COLPM0 for the border and background (Playfield 0 value pixels) rather than COLBK. Player/Missile graphics display properly with the exception that Player/Missile 0 are not distinguishable from the background pixels, since they use the same color register, COLPM0. The Playfield pixels using the Player/Missile colors are modified by priority settings as if they were Player/Missile objects and so can affect the display of Players/Missiles. (See discussion later about Player/Missile/Playfield priorities). The Playfield pixels using Player/Missile colors do not trigger collisions when Player/Missile objects overlay them. However, Player/Missile graphics overlapping Playfield colors COLPF0 to COLPF3 will trigger the expected collision. 16 Colors This mode uses the COLBK register to specify the luminance of all Playfield pixels (values 1hex/1dec through Fhex/15dec.) The least significant bit of the luminance value is not observed, so only the standard/CTIA 8 luminance values are available (, , , , , , , ). Additionally, the background itself uses only the color component set in the COLBK register. The luminance value of the background is forced to 0. As with the Luminance mode indirection is disabled and pixel values directly represent a color. Note that the color component of the background also merges with the playfield pixels. Colors other than black for the background reduce the overall number of colors displayed in the mode. Player/Missile graphics (without the fifth Player option) display properly in this mode, however collision detection with the Playfield is disabled. Playfield priority is always on the bottom. When the Missiles are switched to act as a fifth Player then where the Missile objects overlap the Playfield the Missile pixels inherit the Playfield pixels' Color