I have written about Wallwisher before – it’s a great way to collect feedback from students or perhaps for them to create a ‘revision wall’ with key facts for a topic. (Note that Wallwisher walls can be a little slow to load).
It struck me recently that it is a very simple way for teachers to create a matching type exercise.
See for example Quadrilaterals – properties.
Only the wall owner can move sticky notes around so this could be used in the classroom as a starter once logged in to Wallwisher.
Another possibility – move the sticky notes to solve the equations.