The open-source platform for desktop entertainment.
Real personality for your computer. Harmless desktop creatures, playful window antics, cursor surprises, and ambient companions — all optional, all reversible, all yours.
100% offline & privacy-first. No accounts. No telemetry. No analytics. Runs entirely on your machine.
- Features
- See it in action
- How It Works
- Why Mischief
- Installation
- Building Experiences
- Security & Privacy
- Transparency
- Repository Structure
- FAQ
- Changelog
- Community & Support
- Author & Maintainer
- License & Disclaimer
| Spin | Dance | Hide | Idle |
|---|---|---|---|
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 |
 |
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Every companion runs playful procedural behaviors like these — spin, dance, hide, peek, pounce, and sneak — right on your desktop.
- Experience Packs — declarative, data-only content anyone can create: characters, antics, ambience, seasonal effects
- Plugin SDK — sandboxed extension host for real logic without touching core
- Events carry priority, conditions, and cooldowns — the companion never spams you
- Intensity levels from Silent to Chaos — you decide how much mischief you want
- The companion reacts to your real work: sleeps after inactivity, yawns when you return, wanders the desktop, perks up when you click it
- Interactive mode — click your companion and watch it react (off by default; click-through preserved)
- Settings window — tune intensity (Silent → Chaos) and personality live, persist your preferences
- 19 Flagship Characters — Zen (Red Panda), Kumo (Cyber Fox), Astra (Stardust Dragon), Barnaby (Capybara), Pippin (Penguin), Pocus (Ghostling), Byte (Vintage Bot), Nami (Sea Otter), Pixel-Rex (Pixel Dino), Lumina (Crystal Phoenix), Mochi (Shiba Baker), Voxel (Mecha Cat), Bramble (Hedgehog), Sola (Sunflower), Whiskers (Cat), Spectra (Ghost), Sparky (Robot), Pixel (Pixel Buddy), and Bloop (Sample Creature) — each with unique species-themed dialogue
- Character-Specific Speech — every companion has its own dialogue pools for petting, idle moments, power events, and more; user-imported companions get a voice that matches their personality
- Anti-Repeat Chatter — a shuffled picker never repeats the same bubble twice in a row, so the companion stays fresh
- Behavior-Aware Reactions — the companion comments on its own antics (hiding, peeking, spinning, pouncing, sneaking, dancing)
- Playful Behaviors — six playful behaviors (hide, peek, spin, pounce, sneak, dance) run for every companion, including custom imports
- Combo Streaks — consecutive pets trigger escalating reactions (Combo x2! 🎉, Super happy!)
- Developer Triggers — IDE save, git commit, and build green reactions for your workflow
- Wellness Reminders — hydration and posture check nudges during work hours, plus deep-focus and weekend greetings
- Every effect is reversible, optional, and transparent
- Manifests validated at load — a strict security boundary before any third-party content runs
- Mischief is a mischievous friend — never malware, never destructive
- No accounts, no telemetry, no analytics — zero network calls by default
- Works entirely offline on Windows, macOS, and Linux
- Pure, tested domain layer (
src/domain/) with Vitest coverage - CI that typechecks, lints, builds, tests, audits dependencies, and scans for secrets
good first issuebugs you can pick up in minutes
Mischief is a lightweight Runtime that loads modular Experience Packs. Packs are data — the runtime decides when and how to show them.
1. LOAD ────► Experience Pack manifest validated (pure, tested domain layer)
│ PASS
▼
2. SCHEDULE ─► events scored by priority, conditions & cooldowns
│ event fires
▼
3. ACT ─────► overlay companion · window antics · cursor effects · speech bubbles
│
4. REVERT ───► every effect is reversible
│ intensity: Silent → Chaos
Each step checks the previous before proceeding. Third-party content is never trusted blindly — validation happens before anything is scheduled or rendered.
| Dimension | Typical prank apps | Desktop pets (Shimeji, Goose) | Mischief |
|---|---|---|---|
| Business model | Ads, bundles, paywalls | Free, often abandoned | Open source, MIT |
| Safety | Irreversible effects | Varies | Reversible + transparent + intensity levels |
| Extensibility | Closed | Limited | Experience Packs + plugin SDK |
| Privacy | Telemetry | Varies | Zero telemetry, offline-first |
| Platform | Single OS | One OS | Windows / macOS / Linux |
| Trust | Unknown binaries | Unsigned | CI-tested, gitleaks-scanned, reproducible |
Installers for Windows, macOS, and Linux are published in Releases. Download the build for your OS, install, and a small companion appears at the corner of your desktop with a tray icon.
Requires Node.js 18+
git clone https://github.com/moiz-za/Mischief.git
cd Mischief
npm install
npm run devA small companion appears on your desktop, and a tray icon keeps Mischief running.
npm run dist:mac # or dist:win / dist:linuxAny data-only pack can become an experience. Start from the reference pack:
examples/experiences/sample-creature/ # a complete working character
examples/plugins/hello-plugin/ # a minimal plugin skeletonNew to the project? Browse the good first issue list — icons and manifest validation are great starting points.
Security is a core design principle, not an afterthought:
- Secret scanning — gitleaks blocks secrets in the pre-commit hook and in CI; the full history is scanned
- Dependency audit —
npm auditruns in CI on every push and gates every release - Pinned, maintained Electron — upgraded and kept current; 0 known vulnerabilities at every release
- Zero telemetry — Mischief makes no network calls by default; nothing leaves your machine
- Private vulnerability reporting — report via the repository's Security tab (see
SECURITY.md)
See Transparency for exactly what Mischief does with your machine.
Mischief is a desktop app that lives on your screen, so you deserve to know exactly what it can and cannot do. This is the whole truth — nothing hidden, nothing "in beta."
| Behavior | Details |
|---|---|
| Reads your cursor position | Moves the companion to follow or wander near it. Position data never leaves your machine |
| Reads system idle time | To know when you've stepped away (so the companion can nap). It does not log what you were doing |
| Draws a small overlay on top of your windows | A 96×96px transparent, always-on-top companion window. It's decorative; it can't read or modify other apps |
| Captures the screen — only when you ask | "Capture moment" grabs ~1.2s or a single frame only when you click the menu item, and saves it to ~/Pictures/Mischief/. There is no background or automatic capture, ever |
| Writes two local files | settings.json (your preferences, mode 0600) and your saved moments in ~/Pictures/Mischief/ |
- ❌ No network calls — Mischief runs 100% offline; it cannot phone home, fetch content, or update itself silently
- ❌ No accounts, no telemetry, no analytics, no advertising SDKs
- ❌ No keylogging — it reads cursor position and idle time only
- ❌ No file access — it reads nothing outside its own install,
settings.json, and the moments folder - ❌ No destructive effects — every effect is reversible, optional, and off by default
- ❌ No third-party code runs — community packs are strict-validated data; the plugin host ships disabled
- Source-first — the app is MIT-licensed and fully auditable at
github.com/moiz-za/Mischief. Build it yourself withnpm run dist:mac(ordist:win/dist:linux) - Checksums — every release attaches a
SHA256SUMSmanifest; verify the installer before running it (shasum -a 256 -c SHA256SUMS) - Signed builds — as of now, release builds are unsigned, so macOS Gatekeeper and Windows SmartScreen will warn on first launch. That warning is the OS being cautious about any new unsigned app, not a sign Mischief is dangerous. Code signing is planned (see Security & Privacy); until then, the source + checksums above are your ground truth
Mischief targets macOS, Windows, and Linux, and every release ships installers for all three (built on native CI runners). The full test suite (pure-JS unit tests for cutout/motion/manifests/behavior/config) runs on Windows, macOS, and Linux in CI, and a Linux boot smoke boots the real Electron app under a virtual display on every push to confirm it starts, loads a companion, and registers its handlers without fatal errors.
We develop and runtime-test on macOS, so it's the most polished. Windows and Linux are continuously build- and unit-test-verified, but occasional cosmetic differences (tray icon rendering, transparent-window behavior on some Linux window managers) may surface there first — report them as an issue and they get fixed fast.
mischief/
├── src/ Electron runtime
│ ├── main.ts tray + overlay host
│ ├── preload.ts secure IPC bridge
│ ├── renderer/ overlay companion (sprite + cutout canvas)
│ └── domain/ pure, tested logic (no Electron)
├── examples/ starter content
│ ├── experiences/ 19 companion packs (zen, kumo, astra, …)
│ └── plugins/ plugin skeletons
├── docs/ experience-pack guide + community docs
├── tests/ unit tests (Vitest)
├── assets/ branding, demos, and icons
└── scripts/ build + hook tooling
Q: Is Mischief malware? A: No. Every effect is reversible, optional, and transparent. It is a mischievous friend, never destructive.
Q: Will it interfere with my work? A: You control the intensity — from Silent to Chaos. Events respect priority, conditions, and cooldowns, so the companion never spams you.
Q: Does it need an account or internet? A: No accounts, no telemetry, no analytics. It runs entirely offline.
Q: Can I make my own companion?
A: Yes. Experience Packs are declarative data — copy sample-creature, tweak the manifest and assets, and load it. No core changes needed.
Q: What platforms are supported? A: Windows, macOS, and Linux. Builds are produced with electron-builder.
Q: How is this different from Shimeji or Desktop Goose? A: They're single-app pets. Mischief is a platform: a small runtime that loads any number of packs, with safety, intensity controls, and an SDK at its core.
| Version | Date | Summary |
|---|---|---|
| v0.4.1 | 2026-08 | Patch release: CI tooling updated to Node 24 GitHub Action majors (no app changes) |
| v0.4.0 | 2026-08 | Playful behaviors (hide/peek/spin/pounce/sneak/dance) for every companion, always-on drag-to-move, anti-repeat + companion-specific + personality-matched speech, behavior-aware chatter, follow-cursor & quick-menu sync, spin/hide animation fixes, removed sound chimes |
| v0.3.1 | 2026-08 | Companion switcher, raster sprite support (PNG/JPG/WebP/GIF), custom companions, import any image with background cutout + expression anchor, import pipeline internals, settings UI layout + repository-boundary fixes |
| v0.3.0 | 2026-08 | 14 character-specific speech pools with unique dialogue, combo streak tracking, developer triggers (IDE save, git commit, build green), wellness reminders (hydration, posture) |
| v0.2.0 | 2026-08 | Settings window (intensity/personality selectors, interactive & cursor-follow toggles, persisted), config manager with fallbacks, GIF moment capture to ~/Pictures/Mischief/, PNG snapshot |
| v0.1.3 | 2026-08 | Personality engine: event bus, intensity levels (Silent→Chaos), weighted behaviors with cooldowns, sleeps/yawns/wanders, interactive pet mode, PNG moment capture |
| v0.1.2 | 2026-08 | Strict manifest validation (security boundary), Experience Pack loader, typed localization (en-US/es/de/fr), themes, runtime loads the Whiskers companion pack, 4 example packs + 2 plugins |
| v0.1.0 | 2026-08 | Initial foundation — Electron + TypeScript skeleton, overlay companion + tray, pure tested domain layer, CI (typecheck/lint/build/test/audit), gitleaks secret scanning, packaging config |
See full CHANGELOG.md for details.
- Report bugs & request features — Open a GitHub Issue
- Questions — GitHub Discussions on this repository
- Contribute — See CONTRIBUTING.md for guidelines; every PR is squashed and CI-gated
- Star the repo — Helps others discover Mischief
Built and maintained by Moiz Zoaib Ali:
- Personal Website: moiz.solutions
- AI Tools Directory: tools.moiz.solutions
- GitHub Profile: @moiz-za
- License: Distributed under the MIT License. Copyright (c) 2026 Moiz Zoaib Ali. See
LICENSEfor details. - Disclaimer: Mischief is provided for entertainment. All effects are reversible and user-controlled; the user remains responsible for how the software is used. Not affiliated with or endorsed by any OS vendor.
Built by Moiz Solutions · Report issues on GitHub