 The matrix of Figure 1.3 is an example of a game in strategic form. At each outcome of the game, which corresponds to a cell in the matrix, the row (column) agent receives as payoff the first (second) element of the ordered pair in the corresponding cell. However, in strategic form games, each agent chooses without first being able to observe the choices of any other agent, so that all must choose as if they were choosing simultaneously. The Figure 1.3 game is a game of pure coordination (Lewis 1969), that is, a game in which at each outcome, each agent receives exactly the same payoff. One interpretation of this game is that Schelling’s spouses, Liz and Robert, are searching for each other in the department store with four floors, and they find each other if they go to the same floor. Four outcomes at which the spouses coordinate correspond to the strategy profiles \((s_j, s_j), 1 \le j \le 4\), of the Figure 1.3 game. These four profiles are strict Nash equilibria (Nash 1950, 1951) of the game, that is, each agent has a decisive reason to follow her end of one of these strategy profiles provided that the other also follows this  profile.[7]