Canvas.setpenopacity(-1);

const turtle = new Turtle();

const step = 0.001;
const scale = 1;
const pointsCount = 45;
let points = [];
const time = -0.5;
let t = time;


function nextX(x, y, t) {
    return x+y*t;
}

function nextY(x, y, t) {
    return y-x*t;
}

function getPoints(t) {
    const newPoints = [];
    let x = t;
    let y = t;
    newPoints.push([x, y]);
    for (let i = 0; i < pointsCount - 1; i++) {
        let newX = nextX(x, y, t);
        let newY = nextY(x, y, t);
        x = newX;
        y = newY;
        newPoints.push([x, y]);
    }
    return newPoints;
}

// init
points = getPoints(t);

function walk(i) {
    t += step;
    let newPoints = getPoints(t);
    for (let i = 0; i < points.length; i++) {
        turtle.penup();
        turtle.goto(points[i][0] * scale, points[i][1] * scale);
        turtle.pendown();
        turtle.goto(newPoints[i][0] * scale, newPoints[i][1] * scale);
    }
    points = newPoints;
    return t < 0;
}