Screamsaver

A Windows parental-control application that monitors microphone volume and blacks out the screen when a child yells too loud during gaming. Configurable via a PIN-protected system tray icon.

How It Works

1. A Windows Service runs in the background as LocalSystem, continuously sampling the default microphone.
2. When the RMS volume exceeds the configured threshold (default: -20 dBFS), the service sends a trigger over a named pipe.
3. The system tray app receives the trigger and instantly covers all monitors with a configurable overlay (color, image, opacity).
4. The overlay fades back out over a configurable duration. A cooldown period prevents repeated triggers.
5. All settings and the stop/pause function are locked behind a parent-set PIN.

Prerequisites

Tool	Version	Notes
Windows 10/11	64-bit	Required
.NET 8 SDK	8.0+	Download
WiX Toolset CLI	v6	See below

Install the WiX toolset once:

dotnet tool install --global wix

Building

Quick build (Debug, no installer)

dotnet build

Build the MSI installer (Release)

The build script publishes all projects as self-contained single-file executables, then compiles the MSI:

powershell -ExecutionPolicy Bypass -File Screamsaver.Installer/Build.ps1

The MSI is written to Screamsaver.Installer/Screamsaver.msi.

Before shipping: Change the compiled-in recovery password in Screamsaver.Core/Security/RecoveryPassword.cs. Run RecoveryPassword.GenerateArrays("YourNewPassword") in a debug session, replace the _encoded and _key arrays with the output, then delete the helper method. Keep the plaintext password in a secure location — it cannot be recovered from the binary without effort.

Installation

1. Run Screamsaver.msi as an administrator.
2. The installer will:
   • Install the ScreamsaverService Windows Service (auto-start, LocalSystem).
   • Install the tray app to %ProgramFiles%\Screamsaver\.
   • Add the tray app to HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run so it starts for all users.
   • Lock the install directory and registry key so standard users cannot modify or delete them.
3. After installation, the tray icon appears in the system tray.
4. Immediately set a PIN: right-click the tray icon → Settings → Change PIN… Enter the recovery password (ScreamsaverAdmin1! by default) as the current PIN, then set a new one. Store the PIN securely.

Uninstallation

Open Add or Remove Programs, find Screamsaver, and click Uninstall. A PIN prompt will appear — the correct PIN or recovery password is required to proceed. If the wrong PIN is entered, the uninstall is cancelled.

Settings

Right-click the tray icon → Settings (requires PIN).

Setting	Default	Description
Volume threshold (dBFS)	-20.0	Loudness level that triggers the overlay. Higher = less sensitive.
Cooldown (seconds)	30	Minimum time between triggers.
Fade-in duration (ms)	0	How fast the overlay appears (0 = instant).
Fade-out duration (ms)	5000	How long the overlay takes to disappear.
Max opacity (%)	100	Peak darkness of the overlay.
Overlay color	#000000	Fill color (click to choose).
Overlay image	(none)	Optional image displayed over the color fill.

Click Preview Overlay to test the current settings without triggering from audio.

Hardening

The app is designed to resist a child attempting to disable it:

Threat	Defense
Killing the tray app	Service watchdog relaunches it within 5 seconds
Stopping the service	Service runs as LocalSystem; requires admin rights
Editing registry settings	HKLM\SOFTWARE\Screamsaver is read-only for standard users
Deleting the install folder	Install directory is read+execute only for standard users
Removing the autostart entry	HKLM Run key requires admin to modify
Opening settings	All tray menu actions require PIN
Uninstalling the app	MSI uninstall requires correct PIN
Forgetting the PIN	Compiled-in recovery password provides last-resort access

Development

Run the service and tray app together without installing:

# Terminal 1 — service runs as console app in debug mode
dotnet run --project Screamsaver.Service

# Terminal 2 — tray app
dotnet run --project Screamsaver.TrayApp

To test with the service registered locally:

# Must be run as Administrator
$exe = "$(pwd)\Screamsaver.Service\bin\Debug\net8.0-windows\Screamsaver.Service.exe"
sc.exe create ScreamsaverService binPath="$exe" start=auto
sc.exe start ScreamsaverService

# Remove when done
sc.exe stop ScreamsaverService
sc.exe delete ScreamsaverService

Project Structure

Screamsaver.sln
├── Screamsaver.Core/          # Settings model, IPC contracts, PIN validation, registry I/O
├── Screamsaver.Service/       # Windows Service: microphone monitor, tray watchdog, pipe server
├── Screamsaver.TrayApp/       # System tray UI: overlay, settings form, pipe listener
├── Screamsaver.UninstallHelper/  # PIN prompt exe invoked by MSI before uninstall
└── Screamsaver.Installer/     # WiX v6 source (.wxs) and build script (Build.ps1)