Made famous by the well renowned Alan O’Donoghue working with students and teachers in schools across the UK, stepped challenges show students the output from a program, but not the success criteria. The challenge is for the students working in a paired-programming approach to reproduce the program only from seeing the output.
This results in a great initial analysis activity while students discuss what they think the requirements are. Having established this, the pairs embark on writing the program. This results in many varied approaches as students interpret the requirements differently. Having completed their program, one of the students from a pair goes to look at the solution another pair created, bringing back something to consider for inclusion in their own program.
Stepped challenges work great as whole class activities.