I started work on what I call the "vector demo." It's a program that draws a line in a 6 by 5 tile box (48 by 40 pixels) in CHR-RAM. The line can be moved around with the d-pad, and can only go down and right on a slope less than 1 (for now). The only problem is, I get a grey screen of nothingness! What is wrong with my code? I'm gong to guess the initialization, but it's worked fine in my other programs. Maybe it's the CHR-RAM writes during VBLANK - if NESASM compiled my zero-page instructions as $00xx the timing's probably off. So what's wrong? Download it here.