!!ARBfp1.0
TEMP output;
TEMP input;
TEMP bright;
TEMP dark;

TEX input, fragment.texcoord[0], texture[0], RECT;

# Subtract color by 0.51 => everything with more then 0.51 will have at least 0 ;
SUB output.rgb, input, 0.51;

# Create a dark color..;
SUB dark.rgb, input, 0.3;
# ..and a bright color ;
ADD bright.rgb, input, 0.3;

# All colors which are < 0 (original color - 0.51 < 0) get a dark color and everything else a bright color ;
CMP output.rgb, output, dark, bright;

MOV result.color, output;
END