I'm working with Turbo C++ in 13h mode (256 colors) and what I want to do is make a function(s) that would either light-up the entire screen (just like turning up the brightness for all colors) or blackout (all colors going to black). So what I want to know is what's a good algorithm for both? I've written a few functions, for example for the light-up function I would just take the current RGB value for a color and increment all three colors by 1, but that tends to mess up the actual picture (like if one of the colors is at the max already then the other two would increase by them selves changing the actual color and not only the brightness). Any good ideas?