Ripples

An attempt at wavefront simulation.

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Canvas.setpenopacity(-0.05);
const iters = 15000000;
const size = 60;
const space = 2;
const segments = 360*30;

const turtle = new Turtle();
const startSide = Math.random() > 0.5;
let ax, ay, j;
let tmp;
let direction = "left";
let otherDirection = "right";
let inside = true;
turtle.penup();
turtle.goto(16, -31);
turtle.seth(45);
turtle.pendown();

function randomStart(n, m) {
    return Math.random() > 0.5 ? (Math.random() > 0.5 ? n : -n) : (Math.random() > 0.5 ? m : -m);
}

function changeDirection() {
    tmp = otherDirection;
    otherDirection = direction;
    direction = tmp;
}

function walk(i) {
    ax = Math.abs(turtle.x());
    ay = Math.abs(turtle.y());
    if (inside && ay >= size && ax >= size) {
        turtle.seth(540+turtle.h());
        changeDirection();
        inside = false;
    }
    else if (inside && ax >= size) {                                                                                                                                                                                                          
        turtle.seth(540-turtle.h());
        changeDirection();
        inside = false;
    }
    else if (inside && ay >= size) {
        turtle.seth(720-turtle.h());
        changeDirection();
        inside = false;
    }
    else if (Math.floor(ay) <= size && Math.floor(ax) <= size) {
        inside = true;
    }
    turtle[direction].call(turtle, 360/segments);
    turtle.forward(space*Math.floor(i/segments)*2*Math.PI/segments/20);
    if (i%segments === 0) {
        turtle.penup();
        turtle[otherDirection].call(turtle, 90);
        turtle.forward(space/20);
        turtle[direction].call(turtle, 90);
        turtle.pendown();
    }
    return i < iters;
}