// Pressing Control-R will render this sketch.
 
void setup() {  // this is run once.   
    // set the background color
    background(255);
    size(200, 200); 
    smooth();
    frameRate(30);
    strokeWeight(10);
} 
float off = 0;
void draw() {  // this is run repeatedly.  
background(255);
 
pushMatrix();
translate(120,0);
rotate(3.14 / 4);
 
off += .1;
for(float x1 = 0; x1 < 120; x1++){
    float x2 = x1 + 1;
    float a1 = off + x1 / 40;
    float a2 = off + x2 / 40;
    float y1 = 20 * sin(a1);    
    float y2 = 20 * sin(a2);    
 
    if((x1 +1) % 31 == 0){
       stroke(255,0,0);
       line(x1,100,x2,y2+100);
       line(x1,100,x2,-y2+100);
    }
 
 
    stroke(128);
    line(x1,y1+100,x2,y2+100);
    line(x1,-y1+100,x2,-y2+100);
}
popMatrix();
 
}