const SZ = 17; // min=10, max=40, step=1

const cell = 200 / SZ

Canvas.setpenopacity(-1);

const t = new Turtle();

for (let y = 0; y < SZ; y++) {
    for (let x = 0; x < SZ; x++) {
        let tile = Math.floor(4 * Math.random()) 
        
        if (tile == 0) {
            t.jump(-100 + (x + 0.5) * cell, -100 + y * cell)
            t.setheading(90)
            t.circle(cell/2, 90)

            t.jump(-100 + (x + 0.5) * cell, -100 + (y + 1) * cell)
            t.setheading(-90)
            t.circle(cell/2, 90)
        }
        else if (tile == 1) {
            t.jump(-100 + (x + 0.5) * cell, -100 + y * cell)
            t.setheading(-90)
            t.circle(cell/2, -90)

            t.jump(-100 + (x + 0.5) * cell, -100 + (y + 1) * cell)
            t.setheading(90)
            t.circle(cell/2, -90)
        }
        else if (tile == 2) {
            let gap = cell / 3

            t.jump(-100 + (x + 0.5) * cell, -100 + y * cell)
            t.setheading(90)
            t.forward(cell / 2 - gap / 2)
            t.penup()
            t.forward(gap)
            t.pendown()
            t.forward(cell / 2 - gap / 2)

            t.jump(-100 + x * cell, -100 + (y + 0.5) * cell)
            t.goto(-100 + (x + 1) * cell, -100 + (y + 0.5) * cell)
        }
        else {
            let gap = cell / 3

            t.jump(-100 + x * cell, -100 + (y + 0.5) * cell)
            t.setheading(0)
            t.forward(cell / 2 - gap / 2)
            t.penup()
            t.forward(gap)
            t.pendown()
            t.forward(cell / 2 - gap / 2)

            t.jump(-100 + (x + 0.5) * cell, -100 + y * cell)
            t.goto(-100 + (x + 0.5) * cell, -100 + (y + 1) * cell)
        }
    }
}