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Scratch's pen feature can be used to create line drawings, and it can also be used to fill the screen with a picture. This article will show some pen art examples, and their scripts, utilizing intrinsic information present within either the Scratch stage combined with other builtin mathematical operations.
Set Up
Please follow the instructions on this page to create the basic pen drawing script. The only block that will be needed is this one:
set pen (color v) to (Equation or Source)
Color
Adding Math
Scratch has many mathematical functions. Although some seem complicated, using them can produce many different results.
Description  Image 

This script produces waves:
set pen (color v) to ((y position) + ((50) * ([sin v] of (x position)))) 

The arctangent function (abbreviated "atan") can be used to make a color wheel like so:
set pen (color v) to (([atan v] of ((y position) / (x position))) / (0.9)) 

This script mixes a color wheel with rings:
set pen (color v) to ((([atan v] of ((y position) / (x position))) / (0.9)) + (distance to (origin v))) 

This script creates wavy rings:
set pen (color v) to ((([atan v] of ((y position) / (x position))) / (0.9)) + ((20)* ([sin v] of ((10) * (distance to (origin v)))))) 
Examples
See more examples of pen art: