Here are a few screen-transition effects obtained by modifying values of margins and line pointer of each modeline. The examples work in 160x144 16-c square pixel "mode" but the code works for all screens (I think) with more than one modeline for display block...

First "screen swipe":

tsweep0

- moving screen
- fixed left margin increments (+-1)

tsweep1:

- static screen
- fixed margin increments (+-1)

tsweep2

- moving screen
- "random" left margin increments (+-1)

tsweep3:

- static screen
- "random" margin increments (+-1)

Don't know if anyone is interested in the code but I'm posting it anyway...

Controls: joy left/right

front.asm and back.asm are the images used for background graphics...

Third: "movable and resizable circular shape"

tcirclem

tcircler

the same as tsquare but with circular shape(although the shape seems a little off...)

The sources aren't commented and may be a bit messy...sorry for that

Amazing!

Yeah, these effects look quite good but the best is that they're quite cheap (about 0.5-1.0 frame)  and don't corrupt the screen buffers so can be used in games. Not much additional memory needed - only the routine and one 256-byte lut. The code is not optimized (the circle one the most).

Here are two more variations:

tsweep4:

- a "noise" animation of screen ends using "random" increments/decrements

tsweep5:

- "random" margin increments/decrements (both margins)
- static screen
- move joystick left and right to animate

tsweep5 could be changed to use fixed increments/decrements

...and one more:

Awesome!