Screen Saver Ideas

[inexorabletash]

A thread for suggestions for screen savers.

A screen saver is a desk accessory that does something interesting with the whole screen. The requirements:

• Main/Aux memory from $800...$1FFF can be used for code/resources.
• If needed, a 16k overlay buffer in main memory can also be used, it just requires restoring from disk afterwards.
• If text/lores/double-lores pages are used they must be saved/restored. See Matrix for an example.
• If hires/double-hires pages are used a full repaint must be triggered on exit. See Melt for an example.
• They should exit on key press or mouse click. Therefore they should poll MGTK for events. See Melt for an example.
• The mouse cursor can be hidden or shown.
• Banking should be restored on exit: LCBANK1 read/write active and ALTZP active.
• Display should be restored on exit: Double-hires active with preferred color mode (via jsr JUMP_TABLE_RGB_MODE)

There are examples of all of these. Adapting demos written outside the A2D ecosystem is relatively straightforward.

[inexorabletash]

Star field / warp speed

[inexorabletash]

Conway's Life - e.g. https://68kmla.org/bb/index.php?threads/game-of-life-for-apple-ii.42543/

[inexorabletash]

Snow - flakes drift down from the top of the screen and accumulate on the top of windows or the bottom of the screen.

[inexorabletash]

Suggested by JaY Edwards: Martymation

These are found on Side B of the Printshop. https://www.youtube.com/watch?v=IYpUuO00cic

Deater did a recent example https://archive.org/details/twitter-1404863184142438400

These work by loading images to both hires screens and doing a combination of page flipping and palette bit toggling, which strongly evokes the palette cycling demos of the late 1980s for 16-bit computers.

The big challenge for these as A2D screen savers is that while $2000-$3FFF main/aux is available (page 1), $4000-$5FFF main/aux is used for critical code (main: the input loop; aux: MGTK).

[inexorabletash]

Suggested by JaY Edwards: https://www.youtube.com/watch?v=XoXOQx5mcNs

by @deater

[inexorabletash]

Suggested by JaY Edwards: http://www.deater.net/weave/vmwprod/apple2_fire/

By @deater

[inexorabletash]

There are also tons of Applesoft BASIC one-liner and two-liner programs (e.g. from Nibble) that do neat things with the screen.

It should be possible to force Applesoft to run in the memory constraints of a DA:

• Save the zero page and text pages contents
• Bank in ROM/main ZP
• Set LOMEM and HIMEM appropriately
• Hook the appropriate I/O routine to capture exiting from BASIC back to the ] prompt
• Load the tokenized program into memory (or maybe feed the text in and have BASIC tokenize it?)
• Invoke the interpreter
• On exit, restore everything

[inexorabletash]

Plasma

• Add a Hi-res Plasma Screen Saver #829
• Add a Lo-res Plasma Screen Saver #828