Reuse: build a scene with a helper

Write one reusable drawing helper and call it several times to compose a whole picture.

Write once, use everywhere

The real power of functions is reuse. Instead of copying the same shapes over and over, write a helper once and call it many times — each call with different inputs. Less code, fewer mistakes, and changes only need to happen in one place.

Below, a single drawTree(x) helper draws a trunk and leaves at a given x. Calling it a few times plants a whole row of trees:

One helper, called four times, builds a little forest.

Spot the repetition

Whenever you find yourself copying and pasting the same shapes with small tweaks, that's a sign to make a function.

Write once, use everywhere

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