definitely a very useful optimization. would evaluating the results of calculations with constants at compile time also be practical? it may make source code easier to read, since one can tell where the numbers came from.

Yay, I like this optimization!  Great job Quigibo!

Amazing work, Quigibo. That was a impressive optimization.  
Is there any main optimizations like that left?

There are many more left.  I only did the most basic of basic look-ahead parsing technique.  Another major optimization will be looking ahead to see if arguments are constant or variable expressions when compiling.  Right now, expressions after each argument are saved as a precaution becasue later arguments might use longer routines that scramble the registers.  But if I can guarantee that all arguments after that point are constant, then I don't need to do all that useless saving.

@DJ, your code probably was optimized.  I had to make the sprite drawing routines slightly larger to accommodate grayscale, however at the same time, there were a couple places that got optimized so it just happened to balance out coincidentally.  

I've been working on the start of a game since yesterday. The first task I undertook was animation of the character you control, as I wanted to get to test out the new 4-level grayscale. The 16x16 sprite has 5 different body positions, with the body outlined in dark gray and filled with light gray, as I plan for the surroundings to be drawn in black and white for contrast. It looks great when he isn't moving much, but when he jumps, the image of him breaks up a lot. When drawn in just 3-level grayscale, it looks much cleaner. Is this just an unavoidable aspect of 4-level grayscale sprites moving quickly?

Below are GIFs of the program displaying 3-level grayscale (above) and 4-level grayscale (below). They play in full speed on my computer, with any luck they will for anyone else viewing them too.

Those look awesome! Great job. Though the 4-level gray scale is a little choppy I do like the little outline around the character.

The only way to make it look cleaner is to update the screen more often between frames (slow it down) becasue 4 bit gray needs to be drawn in the same place for 3 frames to guarantee a cycle through all the gray.  That's becasue the pixels stay black for 0,1,2, or 3 times during the duration of 3 frames to get the white, light gray, dark gray, and black.  By contrast, 3 bit gray only needs to be drawn 2 times between frames for a smooth animation (but still, more looks better).  That's why most 4 color grayscale games, like desolate, don't generally feature a lot of motion at once.

Raytracing or Raycasting? Raytracing is much more complex, and I do not know of any raytracing ever done on a calculator.

Raytracing or Raycasting? Raytracing is much more complex, and I do not know of any raytracing ever done on a calculator.

Whoops my bad. I deliberately looked the two up before I posted that to make sure I didn't mix them up, but I guess I mixed them up anyways lol.