Why A Retractable Pen?
Click! Click! Retractable pens feature a very clever mechanism called a "push-push" mechanism. This type of mechanism exists in many forms: old push light switches, cabinet latches, sim card readers, and more. But this is probably the most recognizable implementation.
The main question: why does the pen tip press out when you push the pen down, but the pen tip retracts when you push down again? Let's get into it.
What is A Push-Push Mechanism?
A Push-Push Mechanism allows the user to toggle between two states (on/off, open/closed) with the push of one input. In this case, the press of the pen moves the pen tip out then back in.
