GRP2 and GRP3 mystery

Any graphics page can be used for any purpose. By default: GRP0: upper screen graphics GRP1: lower screen graphics GRP2: none GRP3: none GRP4: upper screen sprites, lower screen sprites GRP5: upper screen BG tiles, lower screen BG tiles But you can use GPAGE, SPPAGE, and BGPAGE to change these.

The reason you're given two extra pages is for page flip buffering and scratch spaces for drawing/compositing graphics, among other things.

And technically it's possible to use all pages at once, if you use separate sprite and bg pages for each screen.

Like when I did GPAGE 2,2 after using sb sprite tool, I got the top screen with the grid.

Like when I did GPAGE 2,2 after using sb sprite tool, I got the top screen with the grid.

Because you can use any graphic page for drawing and displaying images. SBGED is programmed to use pages 2 and 3 for its interface because they wanted to make the images on 0 and 1 editable (since those pages are more likely to be used.)

It would definitely be possible for them to only destroy one graphics page for the interface

It would definitely be possible for them to only destroy one graphics page for the interface

they were lazy