Motion Sense on Pixel 4 (Soli)
Control your phone with natural movement: radar-based gesture and presence sensing.
Design Lead
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2018–2020
Shipped the first radar-based gesture & presence input on a consumer phone; new interaction modality (aware → anticipate → respond).
Problem
Soli is a miniature radar that senses spatial relationships, presence, and fine movement. The challenge on Pixel 4 was to turn that sensing into a way to control a phone with natural movement, a new input modality with no established UX conventions. Radar is invisible, so the hard problems were legibility and trust: people had to understand when the phone was sensing them, what gestures it recognized, and how to rely on an input they couldn’t see.
Approach
I built the interaction around three states: Soli is aware of your presence, anticipates when you want to interact, and recognizes and responds to your gestures. That aware-anticipate-respond model made an invisible input legible. To support it, I defined a library of recognized movements and a design system so the feedback stayed consistent across every experience Motion Sense powered.
Process
Presence
As you reach for Pixel 4, Soli turns on the face-unlock sensors in anticipation, so the phone unlocks as you pick it up, in one motion rather than two.
Gestures
Wave above the screen to snooze an alarm or silence a call; tap or swipe to pause or skip music. Each gesture maps to a moment when reaching past the screen is more natural than touching it.
Interaction model
Aware, anticipate, respond: the model for how Soli senses a person and reacts, and the backbone the individual gestures were designed against.
Movement library
A library of recognized movements and a supporting design system kept gestures and feedback consistent, and gave other teams a foundation to build radar interactions on.
Outcome
Shipped as Motion Sense on Pixel 4: the first radar-based gesture and presence sensing on a consumer phone. The work left a reusable interaction framework, movement library, and design system for an entirely new input modality.
Pixel 4 teaser
Phone unlocks as you reach for it
Wave to skip to the next song
Snooze alarms without fumbling for your phone
Visual feedback system
Lessons
An invisible input lives or dies on legibility: people only trust what they can understand. Defining the states and feedback first, before the individual gestures, is what made radar sensing usable rather than just novel.