Ragnarok. The fabled end of the world, when Norse gods and monsters fight for supremacy. As Thor, you must stop a giant serpent from digesting Valhalla by channeling Odin’s lightning along the length of its body. But can you find a path that will completely destroy it?

The video briefly references the case when all the nodes in a graph have an even number of edges. Will the starting and ending point of an Eulerian circuit on such a graph always be the same node? How do you know? Try drawing examples of other graphs with this property, and see whether the starting and ending points of an Eulerian path are indeed always the same.