The document presents a three-state model for tools, where tools are either affecting a target, not affecting a target, or in a pre-affect state. It discusses examples such as a ballpoint pen and computer cursors, emphasizing that each state has unique functionalities. The document notes that while ideally all inputs should support all three states, there are exceptions, like fingertips on touch screens, which can only press or rest off buttons.

1. The Three-State model
for tools
Ajay Ganapathy

2. Tools affect targets
• At any given time a tool is either affecting a
target, or it isn’t.

3. Tool Ballpoint pen Vehicle ______? _____?
affecting writing moving fired _____?
not
capped off holstered _____?
affecting

4. The third state
• Some tools have a distinct state when they
are about to affect their target.

5. Tool Ballpoint pen vehicle ______? _____?
affecting writing moving fired _____?
about to
exposed idling loaded _____?
affect
not
capped off holstered _____?
affecting

6. On computers:
• A cursor can be deactivated, hovering, or
activated. Each state carries with it unique
affordances.
• A fingertip can press a button, rest on the
button, or rest off of the button.
• Ideally, all inputs should support all three
states. However, this is not always the case.

7. Exceptions:
• A fingertip on a touch screen can’t rest on
a button. It can only either press the button
or rest off of the button.