What made iWork a success—and helped re-launch Apple—was the fact that Pages could open and save most Word files; Numbers could open and save most Excel files; and Keynote could open and save most PowerPoint presentations. Apple did not attain this compatibility through Microsoft's cooperation: it attained it despite Microsoft's noncooperation. Apple didn't just make an "interoperable" product that worked with an existing product in the market: they made an adversarially interoperable product whose compatibility was wrested from the incumbent, through diligent reverse-engineering and reimplementation. What's more, Apple committed to maintaining that interoperability, even though Microsoft continued to update its products in ways that temporarily undermined the ability of Apple customers to exchange documents with Microsoft customers, paying engineers to unbreak everything that Microsoft's maneuvers broke. Apple's persistence paid off: over time, Microsoft's customers became dependent on compatibility with Apple customers, and they would complain if Microsoft changed its Office products in ways that broke their cross-platform workflow.