var numLines = 12;

var lineLength = 150;

var lines = [];

var radius = 10;

​

function setup() {

  createCanvas(640, 480);

  for (var i = 0; i < numLines; i++){

    lines[i] = [];

  }

}

​

function draw() {

  if (boolDoRefresh){

    background(255,250,240);

    for (var i = 0; i < numLines; i++){

        var centerX = random(width);

        var centerY = random(height);

        var angle = random(TWO_PI);

        var x1 = centerX - lineLength*cos(angle);

        var y1 = centerY - lineLength*sin(angle);

        var x2 = centerX + lineLength*cos(angle);

        var y2 = centerY + lineLength*sin(angle);

        line(x1,y1,x2,y2);

        lines[i][0] = x1;

        lines[i][1] = y1;

        lines[i][2] = x2;

        lines[i][3] = y2;

    }

    for (var a = 0; a < numLines-1; a++){

      for (var b = a+1; b < numLines; b++){

          x1 = lines[a][0];

          y1 = lines[a][1];

          x2 = lines[a][2];

          y2 = lines[a][3];

          x3 = lines[b][0];

          y3 = lines[b][1];

          x4 = lines[b][2];

          y4 = lines[b][3];

          ua = ((x4-x3)*(y1-y3)-(y4-y3)*(x1-x3))/((y4-y3)*(x2-x1)-(x4-x3)*(y2-y1));

          ub = ((x2-x1)*(y1-y3)-(y2-y1)*(x1-x3))/((y4-y3)*(x2-x1)-(x4-x3)*(y2-y1))

          if (ub >= 0 && ub <= 1 && ua >= 0 && ua <= 1){

            interX = x1 + ua*(x2-x1);

            interY = y1 + ua*(y2-y1);

            fill(255,0,0,100);

            circle(interX,interY,radius*2,radius*2);

          }

      }

    }

    boolDoRefresh = false;

  }

}

​

function mousePressed(){

  boolDoRefresh = true;

}