Blog · Design
Pie menus were right. They needed a job.
In 1988 a group at the University of Maryland put pie menus up against ordinary linear menus and measured what happened. Items arranged around the pointer, each the same short distance away, were faster to hit and produced fewer errors. The paper is short and the result is not subtle. Then nothing much happened. Menus stayed vertical lists.
The reason is not that the research was wrong. It is that a pie is a bad shape for the things menus usually hold. A menu has twenty commands, and you can fit about eight around a circle before the wedges get too thin to aim at. Worse, the items are abstract: Paste Special has no natural direction, so you have to learn where it lives. Radial menus survived in the two places those problems do not apply. A handful of tools in a 3D package. A weapon wheel in a game. The rest of the desktop stayed as lists.
The shape was waiting for the right list
Your open windows are a list with none of those problems. The items are not commands you must memorize; each one carries its own icon, and a browser window carries the icon of the site inside it. The order is not arbitrary; it is recency, which is the order you already hold in your head. And the moment you want one, your hand is usually on the mouse and your eyes are usually where the pointer is.
That is the situation pie menus were built for. Fitts's law says the time to reach a target grows with distance and shrinks with size. A pie puts every target the same short distance away, and a wedge gets wider as you move outward, so the target grows as you approach it. A list of stamps in Mission Control is the opposite on both counts.
The count problem, solved by a curve
The one remaining objection is the count. Three windows on a laptop; thirty on a desk with two displays. A circle cannot serve both. A spiral can. The inner turn holds what you touched last. Everything else winds outward, still around the pointer, still ordered by recency. The window you are most likely to want is the closest card, and it is already selected when the spiral opens, so the common case is hold, release, done.
When the case is less common, tap instead of hold and the spiral stays. Move the wheel to walk the cards. Type a few letters to skip the walk. Right-click a card for Move to Display or Full Screen. None of that requires leaving the shape.
If you would rather have a plain ring, Circular is a setting. If you want to see the windows rather than their icons, Strip, Grid and List show previews. The spiral is the default in VortexFlow because it is the shape of the question you are actually asking, which is "what did I just have open?"
Switching windows is the job the pie was waiting for.