// UNIT 2 – Variable Toy
// Title: First-Order Hilbert Curve (Explicit Sequence)
//
// PSEUDOCODE (explicit instructions, no recursion or loops)
//
// Define step length (step)
// Move to starting position (bottom-left of curve)
// Face upward
// Move up by step
// Turn right and move by step
// Turn right and move down by step
//
// This produces the first-order Hilbert curve: a centered “U” shape.
//
// Later units (loops/recursion) can build higher-order curves
// by repeating this shape inside itself.

// Turtletoy setup
Canvas.setpenopacity(1);
const turtle = new Turtle();

// --------------------------------------------------
// Variables controlling geometry
// (these make size and placement easy to adjust)
let step   = 80;     // length of each segment
let startX = -40;    // bottom-left start coordinate
let startY = 40;

// --------------------------------------------------
// Initial positioning
turtle.penup();
turtle.goto(startX, startY);
turtle.pendown();

// --------------------------------------------------
// Ordered movement sequence
function walk(i) {

    // Step 0: face up + rise to top-left cell
    if (i === 0) {
        turtle.left(90);
        turtle.forward(step);
    }

    // Step 1: face right + move to top-right cell
    else if (i === 1) {
        turtle.right(90);
        turtle.forward(step);
    }

    // Step 2: face down + return to bottom-right cell
    else if (i === 2) {
        turtle.right(90);
        turtle.forward(step);
    }

    // Stop after the third segment
    return i < 2;
}