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What is Spank?

Spank is a CLI tool that turns your MacBook into a responsive audio experience. When you slap your laptop, it yells back. Built using the Apple Silicon accelerometer (Bosch BMI286 IMU), Spank detects physical impacts and plays audio responses in real-time.
“this is the most amazing thing i’ve ever seen” — @kenwheeler

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Key features

Direct hardware access

Reads accelerometer data directly via IOKit HID with no separate sensor daemon required

Single binary

Self-contained executable with embedded audio files and zero external dependencies

Multiple modes

Choose from Pain (default), Sexy (escalating), Halo (gaming), or Custom (your own MP3s)

Configurable sensitivity

Adjust detection threshold from light taps to heavy impacts

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How it works

Spank uses a sophisticated detection pipeline to identify physical impacts:
  1. Hardware access: Reads raw accelerometer data directly from the Apple SPU sensor via IOKit HID (requires sudo)
  2. Signal processing: Runs vibration detection algorithms (STA/LTA, CUSUM, kurtosis, peak/MAD) on the 3-axis accelerometer stream
  3. Event detection: Identifies significant impacts above the configured amplitude threshold
  4. Audio playback: Plays an embedded MP3 response with 750ms cooldown to prevent rapid-fire playback
The detection runs at 100Hz polling rate (every 10ms) with sophisticated filtering to distinguish intentional slaps from ambient vibrations.

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What makes Spank unique

Zero dependencies: Spank is distributed as a single binary with all audio files embedded using Go’s embed.FS. No installation of additional packages or audio libraries required. Real-time performance: Processes accelerometer samples in batches of up to 200 per tick, ensuring responsive detection even under heavy system load. Intelligent escalation: In sexy mode, Spank uses an exponential decay algorithm (30-second half-life) to track slap intensity over time. The more you slap within a minute, the more intense the audio response becomes, with 60 levels of escalation based on a 1-exp(-x) curve mapping. Production-ready: Built in Go with proper signal handling, graceful shutdown, and structured error reporting. Can run as a launchd service for boot-time startup.

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Use cases

  • Entertainment: Turn your laptop into an interactive toy
  • Frustration release: Physical feedback when your code won’t compile
  • Ambient awareness: Audio confirmation that your laptop detected an impact
  • Custom notifications: Use --custom mode to play your own audio triggers

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System requirements

Spank requires macOS on Apple Silicon (M2+) and sudo access for IOKit HID accelerometer access.
  • Operating system: macOS on Apple Silicon
  • Chip: M2 or newer (uses Bosch BMI286 IMU)
  • Permissions: sudo/root privileges for IOKit HID access
  • Architecture: arm64

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Next steps

Installation

Download the binary or build from source

Quickstart

Get to your first successful slap detection

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