When you have a group of people and you want to generate some fresh ideas together.

Evolve ideas by iterating them quickly within a group.

1. Give each person a sheet of paper and ask them, with the paper in portrait orientation, to write their challenge right at the top.
2. Ask them to fold their paper so it's divided into four equal horizontal sections.
3. Ask them to draw/explain their initial idea in the top section of the paper.
4. After a fixed time period, everyone passes their paper to the person to their left.
5. The next person should look at the previous idea and iterate it, drawing their new version in the next section of the paper.
6. Carry on doing this until all the sections of the paper are full.
7. A variation is to ask each person to additionally include a statement about why the last idea would fail.

This one is tricky (but not impossible!) to do remotely. If you do want to try it out remotely then leave extra time to allow people to photograph their work and upload it to a shared space or whiteboard.