I mentioned I liked line art. Moving the project from paper to computer is also something I like.
Students begin by trying it out on paper. All of them notice a pattern as they move the ruler down and right. But many do not see what is actually happening with the co-ordinate pairs they are joining together. So the next step is trying it out in Scratch. After we talk about the different ways that you can move in scratch and how pen down and pen up work I ask them to make a block that duplicates the first line they drew with pencil and paper.
They continue adding line segments and notice a pattern and that one coordinate is incrementing while the other is decrementing. At this point we started talking about how the coordinates vary and introduced variables. With variables the code could be simplified. After a few questions, answers and trials students simplified the code.
The next step was to have them use what they learned and make it work in all four quadrants. I this example this continues forever changing color as the lines are drawn. Part of that is shown below.
