Bezier. Using processing.js library.

bezier.js

void setup () {
  size(1024, 576);
  noFill();
  smooth();
  colorMode(HSB, 270, 100, 100);
  frameRate(10);
}

void draw () {
  background(0);
  for (int i=0; i<150; i++) {
    strokeWeight(2);
    stroke(random(360), random(90), random(100));
  bezier(
    random(  0,  512), random(  0, 144), 
    random(512, 1024), random(144, 288), 
    random(  0,  512), random(288, 432), 
    random(512, 1024), random(432, 576));
  bezier(
    random(  0,  512), random(432, 576), 
    random(512, 1024), random(288, 432), 
    random(  0,  512), random(144, 288), 
    random(512, 1024), random(  0, 144));
  }
}