I have a twitter, but I don't tweet, I just follow other people

Ah interesting!  Well to get better grey, not only should you make sure you actually are matching the refresh rate of the screen, but you also probably should try to get dither to work.  Greyscale works because the average color over the course of several frames of animations is not a black or white color.  Dither increases greyscale quality because the average color of a section of screen is made to be grey in every single frame, not just over the course of many frames.  In addition, every pixel of the same color must be dithered in the same rate and in a constant fashion so splotches don't appear. 

For example, you noted that 50% dithering worked really well, correct?  This is where you would draw a checkerboard one frame, and then draw a shifted checkerboard the next frame such that you drew on all the pixels that were not drawn on the previous.  In this way each frame contains 50% black and 50% white, and over the course of many frames all pixels get an even and consistent distribution of black and white. 

Doing this with 33% and 66% (as 4level has 4 color, 0% 33% 66% and 100%) is a bit trickier, but still can be accomplished.  If we look back on our checkerboard example, we can look at the checkerboard as consisting of sections of 2x2 pixels like so:

10      01
01      10
The first and second frame work together to each contain 50% grey.  With 4 level greyscale, we need to make a larger box:

100     010     001
010     001     100
001     100     010
This represents the 3x3 box of 33% grey.  There are 3 steps to this animation, and therefore achieving 33% (1/3) grey is easy.  As you can see, each pixel is on only once in the course of the animation, and the frames are displayed in an orderly fashion, which makes everything look smoother.  66% grey would be achieved in much the same way.

Now the tricky part is this; When you are making your greyscale drawings, you are not going to be making them out of 3x3 blocks.  What you need to do is imagine the 3x3 blocks span all the way across the screen.  An array of 3x3 blocks for each color.  1 repeating pattern for 0% 33% 66% and 100%.  Whenever you want to color a pixel, you select the pixels from the 3x3 block that corresponds to that pixel.  If you wanted to color the pixel at (1,1) to 33% grey, it's color pattern would be 1 on the first frame of animation, and 0 on the second and third.  The pixel at location (4,0) however, would have the pattern 0,1,0.

Using this technique, coupled with matching the refresh rate precisely, can lead your greyscale images to be smooth and as least flicker-y as possible.

Quote from: Builderboy on December 29, 2011, 02:34:19 pm

Quote from: Deep Thought on December 14, 2011, 08:02:13 pm

X/100 to sub(X is a very useful one.

Might as well do .1X since sub() is a 2 byte token

That divides by ten, not 100.

Oh right! Didn't see that there

Builderboy, a friend of his and I played some Left for Dead 2 today I was the only one not to make it

That was lots of fun!  We should do it again soon Later after you left, my friend left me and the two other computers to die But then I did the same to him!

You should check out the new features on the newest version, there is already a switch command

There are indeed many routines to quickly fill the screen with black.  Runer's is possibly the fastest and most optimized as well

Progress is pretty slow, I have been focusing on some other projects of mine recently, but PortalX is not forgotten!

I would suggest not including them at all, as it is smaller, faster, and provides more compatibility to simply let the user take care of clearing and displaying the screen themselves.