While reading Brent’s description of how he programmed in the 90s using UserLand Frontier I immediately thought of NewtonScript. Apple had much innovation in Newton that got overlooked and how apps were developed and ran on the operating system is one. Newton OS even had a database based file system that optimized sharing across applications to prevent redundancy. I think the Newton files system was not only needed due to the constraints of limited physical storage but also to enable fast and easy application development like Brent describes.