it does 180 the first chunk of code to get "One good turn"
then does another 90 in second chunk of code to get the image showing.
So total of 270 degrees.
Depending on what you want you can just use the first or 2nd chunk.
I think you probably just want the 2nd chunk of code if you want to rotate an image from invisible (completely flat where you're looking at the edge of image) to when the image is fully showing.

I would like it differently:

if 0 degrees = completely visible
and 90 degrees = completely invisible

so that the transition would look like this;
A (top / start layer) from 0 to 90 + B (bottom / end layer) from 90 to 0 (and frames arranged in order from bottom to top)

You can change the top chunk of code to go from 0 to 90 (90 range) instead of currently from -90 to 90 (180 range)

0 is completely visible by the way, 90 is completely invisible.

I didn't do it for my code because I don't have a background but had to work before and after image and didn't want the image to rotate such that it would reveal some sort of background other than my before and after images.

The one good turn does some funky operation.
Let me make another version with what I mean for you.

please see version 11. Will transition by 180 rotation from first layer (top layer) to 2nd layer over in this case just a black 3rd layer.

Thank You very much - now it's exactly what I wanted

right on! I was unsure of what you wanted at first. but once the communication was there I knew what to do... no guess work.

Thanks for requesting it btw, it helped relieve me from the one script/day itch hehe

Rel. 6

- error repair related to MathMap.
Expressions (*.mm, *.mmc) are registered in the PDB exactly according to the file name (differently than plugins *.exe, *.py, *.scm )- and the change in its name without changing the pdb procedure call causes an error, eg: separating the name with a space;

- add efect: Rotation Transition
based on plugins by Tin Tran: fade_frames.py version 11 https://gimplearn.net/viewtopic.php?f=3&t=2369

- add efect: Zoom and Rotate (from Outer to Inside) - because not everyone has MathMap installed,
based on plugins by Tin Tran: Animate Newspaper Headlines.py https://gimplearn.net/viewtopic.php?f=3&t=1661

Waiting for Your ideas (that maybe inspire TT to write the code) a bit of classics

For starters: Puzzle

Rel 7: Add efect:PUZZLE SHAPE: SQUARE/CURVED type: regular/shuffle

based on script Puzler.scm by Graechan
http://gimpchat.com/viewtopic.php?f=9&t=6567&start=0

and script-fu-sg-shuffle-layers by Saul Goode
http://gimpchat.com/viewtopic.php?f=9&t=6708

These scripts have been collected to one (Slideshow.scm) and are not registered in the GIMP menu
(and another pdb and they do not clash from originals *scm.)

If there are no new ideas , it's time for classic effects again

Rel 8.

Add efect:

- MELT ME based on script gimp_melt_me_animation_script_by_fence_post.scm by Art Wade
https://www.deviantart.com/fence-post/art/GIMP-Melt-Me-Animation-Script-85164638,

- MAP FOLD EFFECT based on script MapFoldAnimate.scm by Tin Tran
https://gimplearn.net/viewtopic.php/Map-Fold-Effect-amp-Animation-Script-by-Tin-Tran?t=557&p=4020

Fun stuff

Are all of these options available in version 8?