Students use matrices and equations to decode a secret message. I used it last year (and am about to use it again) and students were actually engaged and enjoyed it. They then are instructed to create their own which levels up the DOK. :) I have them work together on the WS mostly to prep them to work together to create their own. But, depending on time and differentiation needs, you can certainly have them stop after the WS or have them fly solo with it. I've used it with Algebra 2 11th graders and will try it with my 9th grade Integrated Math 1 students this year.