With each Scratch project I assign to my high school students, I prepare a rubric. On one side, the project requirements are listed. These are generally listed in a short, bulleted list format which make them easier to follow. Several of my students are on IEP's and so this approach makes it easier for alll students to follow.
On the reverse side of the assignment is the grading rubric. This allows the student to know, before beginning, exactly what I am grading on. It also eliminates any confusion about what I am looking for.
I keep my rubrics simple, 2, 1, 0. Either they complete the task correctly, they attempt the task but have some errors, or they don't attempt the task at all.