“It used to be that the mark of a ‘fun’ office was a foosball table crammed into the break room. But Slack makes the workspace itself feel like a game.” It’s a chat program with an excellent UI that came along at just the right time. It distracts you from your work and it also keeps you at work all the time. Slate’s Amanda Hess on how a simple program with a big valuation is changing office culture.