The overall goal in the workshop is not to come up with a concept but to score the most points. With the first assignment groups can earn points by solving the puzzle as quickly as possible. The first receives three (mushroom) points, the second two, and the third one.
With the other three or four assignments, teams have to award points to each other. After each assignment, teams give a short pitch, and after that everybody gets some time to discuss the ideas and give points by handing over point cards (see picture) to the facilitators. This not only fosters competition (and thus some engagement), it also enables that participants listen to each other and discuss and reflect on the ideas of others.
As a facilitator you can decide whether you want to make the scores known in between or not until the end. The first creates for strategic behavior (by awarding points to those who are less likely to win) but gives feedback which could increase the engagement of participants. I always prefer to make them known in between.
Additionally, to prevent strategic behavior to some extent and ensure that everybody is able to win until the end, I increase the to be awarded points at each assigment.