I don't know much how nitacku does it, he would need to explain if he even visits the forums at all, but it's about switching pixels from white to black very quickly and make sure that not all pixels switch at the same time. I generally recommend 3 level grayscale when it comes to BASIC, since it's less flickery on slower models. The following tutorial is outdated but it shows how 3 level grayscale tiles should be done http://www.omnimaga.org/index.php?action=downloads;sa=view;down=166

Basically you got a picture of the tile where the gray area is a checkered pattern made of white and black pixels, and another picture where only the gray areas are present, as black pixels. Let's say pic1 is the black/white areas and the checkered pattern for the gray area and that pic2 is the gray areas only in black. Your code will look like this:

real(3,1,0,0
While 1
*line of code*
real(3,2,3,1
*line of code*
real(3,2,3,1
*line of code*
real(3,2,3,1
*line of code*
real(3,2,3,1
*line of code*
real(3,2,3,1
[...]
End

Lines of code can be anything providing it's not something that takes a while to process, like a Goto or a line containing more than 1 rand instruction or storing a big string. You need a real(3,2,3,1 command after every line of code, except that if you got something like A+1->A:B+1->B I would recommend putting none between both, because it may be faster than the LCD can handle, causing more flicker. Also if you need to display other sprites it's ok, just make sure there's a real(3,2,3,1 between every real(1 lines of code. To erase them just xor them with the same sprite or do a real(3,1,0,0 command before displaying them again (if it kills the grayscale just add a real(3,2,3,1 before the real(3,1,0,0 or get rid of the one alerady there)

This might also help
http://tibasicdev.wikidot.com/xlib-tutorial#toc6

Reuben used this method. In fact the prgm contained in my old gs tutorial from 2004 is Reuben Walking engine in a very early stage of developpment

moved to calculator help and support

I hope you aren't planning to revive every old topic on the forums, though

ok i am fine as long as there's a reason to revive them

Those xlib commands are not complete and there should only be 1 command in the loop.

Try this instead:

real(1,0,0,2,16,1,0,0,0,0,0
Repeat 0
real(1,0,0,2,16,2,0,0,3,0
End