The first mouse was a simple one-button box, its technology patented under the name of an “x-y position indicator for a display system.” But it turned a computer’s screen from something like a high-tech sheet of paper to a full-fledged space with its own geography, setting the stage for the changes to come.

Many early graphical interfaces were built with powerful layered sets of commands, which users could switch between by activating different “modes.” Modes were a huge element of Engelbart’s vision — a way to achieve vastly augmented intelligence.

During the Lisa’s development, interface designer Bill Atkinson took inspiration from the MIT Spatial Data Management System, a personalized computing environment known as “Dataland” with a map that users could fly over using a joystick.

As the Lisa team worked to nail down its design, they stumbled across a 1980 IBM research concept called Pictureworld, which imagined a then-nonexistent powerful computer that hewed as close to a desktop as possible: you wouldn’t just hit send on an email — you’d put it inside a virtual envelope and drop it in an outbox.

The constant prompting, wrote designers Roderick Perkins, Dan Smith Keller, and Frank Ludolph in a 1997 retrospective, “made users feel that they were playing a game of Twenty Questions.” They raised their concerns with Atkinson, and the group workshopped an alternative that drew from Dataland and Pictureworld, then brought it to Lisa engineering manager Wayne Rosing.

Rosing didn’t want other teams to start adding new systems, and according to Herzfeld, he also had a bigger fear: if Apple co-founder Steve Jobs learned about the idea before it actually functioned, he might delay the entire schedule to work it out.