Pie menus are circular popup menus.
"Linear pull down menus are like climbing ladders to get where you're going... pie menus are like rooms with doors leading off in different directions. Navigating a tree of nested pie menus is like running around a building or an adventure game. You can learn how to get to a certain selection, by remembering a spatial path from room to room. Then you just move the mouse along that path, clicking through each door, and you're there." - Don Hopkins
Pie menus are faster to select from due to the large slices near the cursor. The linear menu bases selection on distance, requiring much hand-eye coordination to select from. Pie menus aid muscle memory because selection is based on direction. Additionally, pie menus only take up screen space when necessary, reducing visual distraction and clutter, unlike toolbars and menu bars.
A disadvantage of pie menus is the limited space on the menu surface. So it is best to limit the number of items in a pie menu to 8 and use submenus for additional items.
Example pie menu bound to the right mouse button.
Example pie menu bound to the middle mouse button.
Optional guide lines show the exact layout of menu items,
Keyboard shortcuts
By combining mouse and keyboard controls a pie menu can be used without moving the mouse,
- press and hold right mouse button,
- use QWE,AD,ZXC, cursor keys or number pad to activate items on the pie menu.