Simple example of drawing a fractal by using a custom block (in "My Blocks") with recursion. To make the tree appear instantly, instead of watching it get drawn: in the scripts canvas, right-click on the block "define (fractal tree)", click "Edit", then enable "Run without screen refresh" (check-box at bottom of pop-up).
Custom blocks are explained in the Scratch Wiki, see https://en.scratch-wiki.info/wiki/My_Blocks Recursion is explained and illustrated in https://en.scratch-wiki.info/wiki/Recursion (the bottom of that page, which also describes the similar tool Snap! , shows the code to make this fractal tree example)
