Have a go at these:
Can you make this into a right-angled triangle by moving just one peg?
Can you enlarge this to the same shape with all the sides twice the length, moving just two pegs?
You could use our interactive geoboard below to try out your ideas.
Choose the size of your pegboard then select the line tool and click on two dots to draw a line between them.
You could set up some similar challenges for your friends, or have a go at More Transformations on a Pegboard.