Counts down the number of scanlines that were drawn during processing of the next frame. The screen has a resolution of 256x224, so at 60 fps, 224 scanlines must be drawn every 1/60th of a second. This count is converted to a percentage to get a sense of the lag. The higher the percentage, the closer we were to not finishing processing in time. If processing does not finish in time, then the game must draw the current frame again and this is a lag frame. If the percentage is a low number, then it is likely the game lagged with most of the work done during the previous frame and a small amount of work left over for the next frame.
0 commit comments