The two components of this dual playfield are treated as any other AMOS Professional screen, and they can even be double buffered or animated with AMAL.
To create a dual playfield screen, simply give the command, followed by the two numbers of the relevant screens, which have already been defined using SCREEN OPEN. Both screens must have the same resolution, and there are some restrictions on the number of colours allowed. Here is a table of the possibilities:
1st Screen 2nd Screen Resolution of both screens 2 colours 2 colours Lowres or Hires 4 colours 2 colours Lowres or Hires 4 colours 4 colours Lowres or Hires 8 colours 4 colours Lowres only 8 colours 8 colours Lowres only
The colours of these screens are taken from the palette of the first screen with colour zero being IF treated as transparent. The first screen makes use of colours zero to 7, while the second screen uses 8 to 15. When you are drawing to the second screen, AMOS Professional will automatically convert the colour index to the appropriate number before using it. This means that colours zero to 7 of the second screen's palette will use colours 8 to 15 of the first screen's palette, in ascending order.
Always make the first screen the current screen when changing the colour settings.
Remember that the automatic conversion process does not apply to assignment statements such as COLOUR or PALETTE.
When using SCREEN OFFSET to position a dual playfield screen, always specify the first screen, and never set screen offsets for both dual playfield screens to zero.
DUAL PRIORITY
instruction: reverse order of dual playfield screens
Dual Priority first screen, second screen
Normally, the first screen of a dual playfield is displayed directly over the second screen. To reverse this order, so that the second screen appears in front of the first, use the DUAL PRIORITY command. Please note that this instruction only changes the order of display, and has no effect on the screen organisation at all, so the first screen in the parameter list is still used for all colour assignments, and with the SCREEN DISPLAY command.
Clearing, hiding and showing screens
Screens can be removed from view by permanently erasing them, or by hiding them away for
later display.
CLS
instruction: clear current screen
Cls
Cls colour number
Cls colour number,x1,y1 To x2,y2