size(200, 200);    
background(0);
stroke(255);
strokeWeight(1);
noFill();

beginShape();
for ( int i = 0; i < 100; i=i+10 ) {
  vertex(50+random(-3,3), 50+i); 
}
endShape(); 

beginShape();
for ( int i = 0; i < 100; i=i+10 ) {
  vertex(50+i, 150+random(-3,3)); 
}
endShape(); 

beginShape();
for ( int i = 0; i < 100; i=i+10 ) {
  vertex(150+random(-3,3), 150-i); 
}
endShape(); 

beginShape();
for ( int i = 0; i < 100; i=i+10 ) {
  vertex(150-i, 50+random(-3,3));
}
endShape();