Mouse wireframe symbol in minigames

[Charano]

So I am trying to get through the sensei training of Yasuke where the sensei tells him to show what he can do with the new katana. You have to follow the minigame prompts. One of them is a line drawing of a mouse with nothing highlighted and I have tried every mouse button and can't get past it. Very un-intuitive icon. What the hell are you supposed to push/do?