### THING

From "Turtle Geometry" by Harold Abelson, 1980

Variations from the book:
"THING1": THING (variation)
"THING2": THING (variation)
"THING3": THING (variation)

```const right = -54; // min=-60, max=60, step=1
const forward = 40; // min=0, max=100, step=5
const repeat = 15; // min=1, max=64, step=1
const scale = 0.6; // min=0.1, max=1.0, step=0.05
const center = 1; // min=0, max=1, step=1 (No, Yes)

const t = new Turtle();

if (center) {
// Compensate for offset by calculating center of regular polygon.

// At full scale, each step travels (125, 25).
// Interior angle is 90 + right.
t.penup();

const d2r = deg => deg / 180 * Math.PI;
const [x, y] = [(125+forward)*scale, 25*scale];
const sidelength = Math.sqrt(x**2 + y**2);
const interior_angle = d2r(90 + right);
const angle_offset = Math.atan2(y, x);
const circumradius = sidelength / 2 / Math.cos(interior_angle/2);

console.debug({x, y, sidelength, interior_angle, angle_offset, circumradius});

t.right(angle_offset);
t.left(interior_angle/2);

console.debug("Offset by", t.pos());

t.degrees();
t.pendown();
}

function thing() {
t.forward(scale*100);
t.right(90);
t.forward(scale*100);
t.right(90);
t.forward(scale*50);
t.right(90);
t.forward(scale*50);
t.right(90);
t.forward(scale*100);
t.right(90);
t.forward(scale*25);
t.right(90);
t.forward(scale*25);
t.right(90);
t.forward(scale*50);
}

function walk(i) {
t.forward(scale*forward); // move forward first to make center calculations simpler
thing();
t.right(right);
return i+1 < repeat;
}```