let angle;
let axiom = "F";
let sentence = axiom;
let len = 100;
let rules = [];
rules[0] = {
  a: "F",
  // b: "FF-[-F-F-F]+[+F+F+F]",
  c: "FF*[*F/F/F]/[/F*F*F]",
};

function generate() {
  len *= 0.5;
  let nextSentence = "";
  for (let i = 0; i < sentence.length; i++) {
    let current = sentence.charAt(i);
    let found = false;
    for (let j = 0; j < rules.length; j++) {
      if (current == rules[j].a) {
        found = true;
        nextSentence += rules[j].b;
        break;
      }
    }
    if (!found) {
      nextSentence += current;
    }
  }
  sentence = nextSentence;
  createP(sentence);
  turtle();
}

function turtle() {
  background(51);
  resetMatrix();
  translate(width / 2, height);
  stroke(255, 100);
  for (let i = 0; i < sentence.length; i++) {
    let current = sentence.charAt(i);
    if (current == "F") {
      line(0, 0, 0, -len);
      translate(0, -len);
    } else if (current == "+") {
      rotate(angle);
    } else if (current == "-") {
      rotate(-angle);
    } else if (current == "*") {
      rotate(angle * 2);
    } else if (current == "/") {
      rotate(angle / 2);
    } else if (current == "[") {
      push();
    } else if (current == "]") {
      pop();
    }
  }
}

function setup() {
  createCanvas(400, 400);
  angle = radians(10);
  background(51);
  createP(axiom);
  turtle();
  let button = createButton("generate");
  button.mousePressed(generate);
}