This staff appears to be made of wood and is approximately a meter long when in its normal form. When activated by Mordo it has several powers. With a strong pull on both ends, the staff expands into a jointed energy nunchaku. It can also extend to an even greater length like a bullwhip. When it impacts a solid object such as a floor, it seems to release a crack of loud energy. Too bad we only ever see it in demo mode.

How might this work as technology?

The staff is composed of concentric rings within rings of material similar to a collapsing travel cup. This allows the device to expand and contract in length. The handle would likely contain the artificial intelligence and a power source that activates when Mordo gives it a gestural command, or if we’re thinking far future, a mental one. There might also be an additional control for energy discharge.

In the movie, sadly, Mordo does not use the Staff to its best effect, especially when Kaecilius returns to the New York sanctum. Mordo could easily disrupt the spell being cast by the disciples using the staff like a whip, but instead he leaps off the balcony to physically attack them. Dude, you’re the franchise’s next Big Bad? But let’s put down the character’s missteps to look at the interface.

Mode switching and inline meta-signals

Any time you design a thing with modes, you have to design the state changes between those modes. Let’s look at how Mordo moves between staff, nunchaku, and whip in this short demonstration scene.

To go from staff to nunchaku, Mordo pulls it apart. It’s now in a dangerous state, so is there any authentication or safety switch here? It could be there, but all passive via contact sensors, which would be the best so it could be activated in a hurry. The film doesn’t give us any clue, really, so that’s an open question.

How does it know to go from nunchaku to whip? It sure would be crappy to bet on a disabling thwack against your opponent only to find it lazily draping over a shoulder instead. (Pere Perez might have advanced ideas, given his ideas on light saber tactics.) Again, this state change could be passive, detecting in real time the subtle gestural differences in a distal snap, which a bullwhip would need, and lateral force, which sets the nunchaku spinning, and adjust between the two accordingly. Gestural and predictive technologies are not particularly cinegenic, so let’s give it the benefit of the doubt and say that’s what’s happening.

A last mode is After Mordo cracks it against the ground, it retracts back to Staff form. This is the hardest one to buy. Certainly it’s a most dramatic ending for Mordo’s demonstration. But does it snap back automatically after it strikes a surface? Automation is not always the answer. Deliberate control would mean Mordo doesn’t have to waste time undoing unwanted automatic actions.

Critical systems must be extremely confident in their interpretations before automation is the right choice.

It might be that this particular gesture is a retraction signal, but how the Staff distinguishes this from a mid-combat strike is tricky. It would have to have sophisticated situational awareness to know the difference, and it doesn’t display this. Better backworlding would point at some subtle gestural signal from Mordo. A double-tightening of his grip, maybe. Or even a double-slight-release of his grip, since that’s something he’s quite unlikely to do in combat.

This is a broad pattern for designers to remember. Inline control signals should be simple-to-provide, but unlikely to occur in literal use. Imagine if the Winter Soldier’s Trigger Phrase wasn’t “Longing, rusted, 17, daybreak, furnace, 9, benign, homecoming, 1, freight car” but instead was the word “the.” He’d be berserking every few seconds. Unworkable. So, if you were designing the Staff’s retraction command gesture, you’d have to pick something he could remember and perform easily, and that would be difficult to accidentally provide.

If Mordo has the staff in the next film, I hope the control modes are clearer and of course well-designed.