var array = ['A'];

var n = 0;

var turtle;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  background(220);

  turtle = new Turtle(0,height);

}

​

function lSystem(input){

  let l = input.length;

  var output = [];

  var rule;

  for(var i = 0; i < l; i++){

    if(input[i] == 'A'){

      rule = ['-','B','F','+','A','F','A','+','F','B','-'];

    } else if (input[i] == 'B'){ 

      rule = ['+','A','F','-','B','F','B','-','F','A','+']

    } else if (input[i] == 'F'){

      rule = ['F']

    } else if (input[i] == '-'){

      rule = ['-']

    } else if (input[i] == '+'){

      rule = ['+']

    }

    for(let j = 0; j < rule.length; j++){

        append(output,rule[j]);

    }

  }

  return output;

}

​

function draw() {

  //noLoop();

  turtle.setWeight(1);

  turtle.setLocation(0,height);

  if(n == 8){

    noLoop();

    for(var j = 0; j < array.length; j++){

      var rule = array[j];

      if(rule == 'F'){

        turtle.moveForward(10);

      } else if(rule == '-'){

        turtle.rotate(PI/2)

      } else if(rule == '+'){

        turtle.rotate(-PI/2)

      }

    }

  }

  array = lSystem(array);

  n++;

}