If you typed in your first BASIC "HELLO" program and made some small modification then there's a chance you've been typing ever since. I've had some time on my hands and read an old tutorial that begged to be inputted and modified.
COMPUTE! September 1983 contains the article "Easy Atari Page Flipping" by Chris Allen. It's a program to demonstrate page flipping on the Atari with plenty of room for experimentation.
My first thought was to smoothly move 2 points along 2 different scan lines at different rates with a line between. That was also my last thought but there was very little left of the original program.
PLOT and DRAWTO was used on the hidden screen while the other was displayed. Erasing the old line before drawing the new one added some complexity to the program. Not enough complexity to strain ATARI BASIC.
The ATR is single density without DOS. It contains the two programs from the article and MYFLIP01.BAS.
If you so choose, start with Chris's program or modify mine in a new direction. Post it in the comment section.
Its just something to do if your locked indoors.