This problem follows on from How Steep is the Slope?

It's easy to draw parallel lines - just check that the gradients match.

 Gradient $\frac{3}{2}$ Gradient $0$ Gradient $-2$

But I'm finding it harder to draw perpendicular lines. Here are my best efforts so far but I don't think they're quite right!

I know that the sides of a square are at right angles, so if I learn to draw tilted squares I may be able to find an efficient method for drawing perpendicular lines.

Experiment with the interactivity below until you can draw squares with confidence.