The visible area can be Moved around the extra-large screen by changing the offset coordinates, and some very smooth scrolling effects are achieved. These can be used for background graphics in computer games, as well as more serious applications like route finders or star constellations.
Manipulating screens
SCREEN CLONE
instruction: clone a screen
Screen Clone number
To create an identical copy of the current screen, and assign this new "clone" with a new screen number, use the SCREEN CLONE command followed by the destination screen number. Here is an example of a multi-cloned screen:
E> Screen Open 0,320,20,4,Lowres
Flash Off
Screen Display 0,,70,,
For S=1 To 7
Screen Clone S
Screen Display S,,S*20+70,,
Next S
Print "Start typing";
Do
AS=Inkey$
If A$<>"" Then Print A$;
Loop
Screen cloning is an ideal technique for two-player computer games, with each player controlling half of the visible display area.
The clone uses the same memory area as the original screen, and will be displayed at the same place as the original. Any of the usual screen operations can be used with the clone, such as SCREEN DISPLAY and SCREEN OFFSET. However, because there is only one copy of the original screen data in memory, it is impossible to use the SCREEN command with the cloned copy.
DUAL PLAYFIELD
instruction: combine two screens
Dual Playfield first screen,second screen
The DUAL PLAYFIELD mode is the equivalent of mixing together two images from separate video cameras, and is achieved by displaying two screens simultaneously at the same x,y- coordinates. Each of the two screens can be manipulated completely independently from one other, and this can be exploited to produce very smooth parallax scrolling. Because the sizes of the two screens can be different, a smaller screen can be scrolled against a larger background screen, creating the parallax effect.