Speaking in an interview at the New Yorker TechFest on Friday, Ive said that his team at Apple had been working on the concept for the last five years. He added that his company “had prototypes” of what a smartphone with a display that nearly entirely covers its front panel and a facial scanner might look like.

“For 99% of the time, it didn’t work for us,” Ive said of the iPhone X prototype processor, according to the India Times, which earlier reported on his comments. “For the vast majority of the development cycle, all we had were things that failed. By definition, if they didn’t fail halfway through, then we’d be done.”

However, as time went on, Apple apparently worked out those problems, ultimately culminating in the iPhone X’s announcement last month.

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Apple’s (AAPL) iPhone X, which was announced alongside the new iPhone 8 and iPhone 8 Plus, is what the company calls the “future” of smartphones. It has a 5.8-inch display with small bezels all around, leaving no room for a physical home button. There are two rear-facing cameras on the back and a glass finish allows for wireless charging support. Apple’s front-facing Face ID scanner is used to verify a person’s identity and allow him or her access to the software or to make a purchase via the company’s Apple Pay mobile-payments service.

All of those features combine to make the iPhone X the most expensive smartphone Apple has ever released with a starting price of $999. A model with 256GB of storage instead of the base 64GB will cost customers $1,149 when the handsets are released on November 3.

Looking ahead, Ive didn’t discuss in detail what he might have planned for new iPhones. He did say, however, that new processor technologies that combine high power and small designs create “opportunities (that) are extraordinary” for future product designs.