Snap’s latest generation of augmented reality Spectacles have been lambasted by one of the engineers who helped to create them. The glasses, revealed earlier this week, were described as “a disaster” by Sterling Crispin, a former design engineer for Snap.

Snapchat’s creator has a new version of its glasses, and a vision for more approachable augmented reality. But it’s still a preview, not a commercial product.

Smart glasses are being touted as the way of the future, but at least one person who’s worked on such projects isn’t quite so sure. A former design engineer at Snap has lambasted the company’s latest augmented-reality Spectacles,