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int i=0;
int p=1;
void setup(){
size(800,600);
}
void draw(){
if(i<height/2){
stroke(255,i,0);
line(0,i,width,i);
i = i + 1;
}
if(height/2<height){
stroke(0,255,p);
line(0,p,width,p);
p = p + 1;
}
}