### EDERA

Edera (revised) by romvise, November 16th, 2005
JS port by @ge1doot, February 2019
contextfreeart.org/gallery2/#design/165

```// You can find the Turtle API reference here: https://turtletoy.net/syntax
Canvas.setpenopacity(-0.5);
// Global code will be evaluated once.
const turtle = new Turtle();
turtle.penup();
/////////////////////////////////////////////////////
const Mat2D = class {
constructor (m) {
this.m = m;
this.type = 0;
}
rotate (v) {
const rad = Math.PI * v / 180;
return new Mat2D([
cos * this.m[0] + sin * this.m[2],
cos * this.m[1] + sin * this.m[3],
cos * this.m[2] - sin * this.m[0],
cos * this.m[3] - sin * this.m[1],
this.m[4],
this.m[5]
]);
}
translate (x, y = 0) {
return new Mat2D([
this.m[0],
this.m[1],
this.m[2],
this.m[3],
this.m[4] + x * this.m[0] + y * this.m[2],
this.m[5] + x * this.m[1] + y * this.m[3]
]);
}
scale (x = 1, y = x) {
return new Mat2D([
this.m[0] * x,
this.m[1] * x,
this.m[2] * y,
this.m[3] * y,
this.m[4],
this.m[5]
]);
}
size () {
const x = this.m[0] * this.m[0] + this.m[1] * this.m[1];
const y = this.m[2] * this.m[2] + this.m[3] * this.m[3];
return Math.sqrt(Math.max(x, y));
}
transform (x, y) {
const m0 = this.m[0] * zoom;
const m1 = this.m[1] * zoom;
const m2 = this.m[2] * zoom;
const m3 = this.m[3] * zoom;
const m4 = this.m[4] * zoom - ox;
const m5 = this.m[5] * zoom - oy;
return [
m0 * x + m2 * y + m4,
m1 * x + m3 * y + m5
];
}
boundingBox (box) {
const p0 = this.transform(0, 0);
const p1 = this.transform(0.5, 0);
const p2 = this.transform(0.5, 0.5);
const p3 = this.transform(0, 0.5);
const minx = Math.min(p0[0], p1[0], p2[0], p3[0]);
const maxx = Math.max(p0[0], p1[0], p2[0], p3[0]);
const miny = Math.min(p0[1], p1[1], p2[1], p3[1]);
const maxy = Math.max(p0[1], p1[1], p2[1], p3[1]);
if (minx < box[0]) box[0] = minx; else if (maxx > box[2]) box[2] = maxx;
if (miny < box[1]) box[1] = miny; else if (maxy > box[3]) box[3] = maxy;
}
};
///////////////////////////////////////////////////////
const minSize = 0.02;
const shapes =  [];
let zoom = 1, ox = 0, oy = 0;
const box = [0, 0, 0, 0];
const fillCircle = m => {
m.boundingBox(box);
m.type = 0;
shapes.push(m);
};
const fillRect = m => {
m.boundingBox(box);
m.type = 2;
shapes.push(m);
};
const rect = m => {
m.boundingBox(box);
m.type = 1;
shapes.push(m);
};
const line = m => {
m.boundingBox(box);
m.type = 3;
shapes.push(m);
};
const draw = shape => {
let d, s;
switch (shape.type) {
case 0:
// fillCircle
s = 0.2 / shape.size();
turtle.goto(shape.transform(0.5, 0));
turtle.down();
d = 1;
for (let a = 0; a < Math.PI; a += s) {
turtle.goto(shape.transform( 0.5 * Math.cos(a) * d,  0.5 * Math.sin(a) * d));
turtle.goto(shape.transform(-0.5 * Math.cos(a) * d, -0.5 * Math.sin(a) * d));
d = -d;
}
turtle.up();
break;
case 1:
// strokeRect
turtle.goto(shape.transform(-0.5, -0.5));
turtle.down();
turtle.goto(shape.transform( 0.5, -0.5));
turtle.goto(shape.transform( 0.5,  0.5));
turtle.goto(shape.transform(-0.5,  0.5));
turtle.goto(shape.transform(-0.5, -0.5));
turtle.up();
break;
case 2:
// fillRect
turtle.goto(shape.transform(-0.5, -0.5));
turtle.down();
d = 1;
s = 0.08 / shape.size();
for (let y = -0.5; y <= 0.5; y += s) {
turtle.goto(shape.transform(-0.5 * d, y));
turtle.goto(shape.transform( 0.5 * d, y));
d = -d;
}
turtle.up();
break;
case 3:
// line
turtle.goto(shape.transform(-0.5, 0));
turtle.down();
turtle.goto(shape.transform( 0.5, 0));
turtle.up();
break;
}
}
const scale = (margin = 0.95) => {
zoom = Math.min(
margin * 200 / (box[2] - box[0]),
margin * 200 / (box[3] - box[1])
);
ox = (box[0] + box[2]) * 0.5 * zoom;
oy = (box[3] + box[1]) * 0.5 * zoom;
};
//
//
//
//
/////////////////////////CFDG ///////////////////////////
// https://www.contextfreeart.org/gallery2/#design/165
const EDERA = m => {
if (m.size() < minSize * 8) return;
fillCircle(m.scale(5));
CIGLIO(m.translate(0, -3));
return EDERA(m.translate(-5, -1).scale(0.9));
}
const CIGLIO = m => {
const r = Math.random() * 2.02;
let weight = 0;
switch (true) {
case r <= (weight += 1):
fillRect(m.rotate(90).scale(1, 0.6));
line(m.rotate(5).scale(4, 1));
return CIGLIO(m.translate(0, -1).rotate(0.5).scale(0.994));
case r <= (weight += 1):
fillRect(m.rotate(90).scale(1, 0.6));
line(m.rotate(5).scale(4, 1));
return CIGLIO(m.translate(0, -1).rotate(0.5).scale(-0.994, 0.994));
default:
fillRect(m.rotate(90).scale(1, 0.6));
line(m.rotate(5).scale(4, 1));
return RICCIOLO(m.translate(0, -1).scale(0.994));
}
}
const RICCIOLO = m => {
if (m.size() < minSize) return;
const r = Math.random() * 1.005;
let weight = 0;
switch (true) {
case r <= (weight += 1):
fillRect(m.rotate(90).scale(1, 0.6));
line(m.rotate(5).scale(4, 1));
return RICCIOLO(m.translate(0, -1).rotate(3).scale(0.994));
default:
fillRect(m.rotate(90).scale(1, 0.6));
line(m.rotate(5).scale(4, 1));
return RICCIOLO(m.translate(0, -1).rotate(3).scale(-0.994, 0.994));
}
}
/////////////////// render scene //////////////////////////////
//
//
//
//
EDERA(new Mat2D([1, 0, 0, -1, 0, 0]));
scale(0.95);

// The walk function will be called until it returns false.
function walk(i) {
const m = shapes.pop();
if (!m) return false;
draw(m);
return true;
}```