In this note we give a version of Hao Huang's proof of the sensitivity conjecture, shedding some light on the origin of the magical matrix $A$ in that proof. For the history of the subject and the importance of this conjecture to the study of boolean functions, we refer to the original paper. Here we only state the main result: Consider the boolean cube $Q_n=\{0,1\}^n$ as a graph, whose edges connect pairs of vertices differing in one coordinate. Then any its induced subgraph on greater than $2^{n-1}$ (the half) vertices has degree of some vertex at least $\sqrt{n}$.