Another concrete example is to define BL and BW as any point at which a game B has a negative or positive expectation. A real-life example of using the A, BL, BW strategy were the MIT blackjack teams of the 80's and 90's.
They had a spotter at each table that would count cards and wait until the odds were in the player's favor before calling in the big money player. Assuming that the bets placed by the spotter are negligible, the the big money player could choose from the following games:
A : Do nothing. E[x] = 0 (break-even)
BL: Play blackjack when the deck favors the casino, E[x] < 0
BW: Play blackjack when the deck favors the player, E[x] > 0
Obviously playing blackjack has negative expectation in the long run, and we could choose another casino game with very-close-to even odds for game A (like Baccarat), rather than doing nothing.