For more flexibility in designing your background display, you can specify two playfields instead of one. In dual-playfield mode, one playfield is displayed directly in front of the other. For example, a computer game display might have some action going on in one playfield in the background, while the other playfield is showing a control panel in the foreground. You can then change either the foreground or the background without having to redesign the entire display. You can also move the two playfields independently. A dual-playfield display is similar to a single-playfield display, differing only in these aspects: * Each playfield in a dual display is formed from one, two or three bitplanes. * The colors in each playfield (up to seven plus transparent) are taken from different sets of color registers. * You must set a bit to activate dual-playfield mode. Figure 3-12 shows a dual-playfield display. Figure 3-12: A Dual-playfield Display In Figure 3-12, one of the colors in each playfield is "transparent" (color 0 in playfield 1 and color 8 in playfield 2). You can use transparency to allow selected features of the background playfield to show through. In dual-playfield mode, each playfield is formed from up to three bitplanes. Color registers 0 through 7 are assigned to playfield 1, depending upon how many bitplanes you use. Color registers 8 through 15 are assigned to playfield 2. Bitplane Assignment in Dual-Playfield Mode Color Registers in Dual-Playfield Mode Dual-Playfield Priority and Control Activating Dual-Playfield Mode Dual Playfield Summary
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