Prevents use of a mouse or touchpad, to encourage testing keyboard navigation.
Web developers must test that all pages and components they create are keyboard accessible (https://www.w3.org/TR/WCAG21/#keyboard-accessible).
In principle, they can do this by simply using only the keyboard and refraining from using the mouse or touchpad.
In practice, however, a developer might find it difficult to break the reflexive habit of reaching for the mouse, e.g. to scroll to and focus on a specific area before testing with the keyboard.
When activated, this extension blocks all mouse interactions within the viewport, so that the developer must use the keyboard to interact with the page.