Squeak Etoys is a "media authoring tool"-- software that you can download to your computer
and then use to create your own media. You can write out your project and share it with others.
Etoys runs on any Mac or Windows machine, as well as on the OLPC XO machine.
It is free.
Find out about Etoys.
Text of this guide (for searching): Script Tile: Pen Use Tiles Mark the Path of the Center of an Object in Motion. Click the green clock to start the script. Create a drawing and open a Viewer for it. Make a script like this one.
Click on basic and choose pen use from the category menu. Drag a penDown tile into the script.
Change false to true; start the script. The penDown tile can remain in the Viewer and will still work if true.
Try other trail styles and colors too.