// You can find the Turtle API reference here: https://turtletoy.net/syntax
Canvas.setpenopacity(.7);

// Global code will be evaluated once.
const turtle = new Turtle();

turtle.penup();
turtle.goto(0,0);
draw=0; // first line is always wrong

//const nx=1; // min=0, max=10, step=1
//const ny=1; // min=0, max=10, step=1
//const nz=1; // min=0, max=10, step=1
const rotatex=240; // min=0, max=360, step=1
const rotatey=170; // min=0, max=360, step=1
const rotatez=150; // min=0, max=360, step=1
const scale=74; // min=0, max=100, step=1
const a=2.8; // min=-10, max=10, step=.1

x=.0
y=.0
z=.0
u=.0
v=.0

// The walk function will be called until it returns false.
function walk() 
{
    for(u=-4;u<=4;u=u+0.04)
    {
        for(v=-4;v<=4;v=v+0.04)
        {

            x=Math.sinh(v)*Math.cos(a*u)/(1+Math.cosh(u)*Math.cosh(v))*scale
            y=Math.sinh(v)*Math.sin(a*u)/(1+Math.cosh(u)*Math.cosh(v))*scale
            z=Math.cosh(v)*Math.sinh(u)/(1+Math.cosh(u)*Math.cosh(v))*scale
    
            // Rotation in x
            xn=x
            yn=y*Math.cos(rotatex/360*2*3.1415)-z*Math.sin(rotatex/360*2*3.1415)
            zn=y*Math.sin(rotatex/360*2*3.1415)+z*Math.cos(rotatex/360*2*3.1415)

            x=xn
            y=yn
            z=zn

            // Rotation in y
            xn=x*Math.cos(rotatey/360*2*3.1415)+z*Math.sin(rotatey/360*2*3.1415)
            yn=y
            zn=-x*Math.sin(rotatey/360*2*3.1415)+z*Math.cos(rotatey/360*2*3.1415)

            x=xn
            y=yn
            z=zn

            // Rotation in y
            xn=x*Math.cos(rotatez/360*2*3.1415)-y*Math.sin(rotatez/360*2*3.1415)
            yn=x*Math.sin(rotatez/360*2*3.1415)+y*Math.cos(rotatez/360*2*3.1415)
            zn=z


            // convert to isometric view, orthographic
            // x' = (x - z) * cos(θ)
            // y' = y + (x + z) * sin(θ)
            // θ = 30° for isometric
            xiso=((xn-zn)*Math.cos(3.1415/6))
            yiso=(yn+(xn+zn)*Math.sin(3.1415/6))
            turtle.goto(xiso,yiso);
        
            if (draw==0) // ignore first line
            {
                turtle.pendown();
                draw=1;
            }    
        }
    }
    return false
}