sample

Halogen Playground

Interactive demo app for the Halogen library. Generate Material 3 themes from natural language prompts and tune LLM parameters in real time.

Features

• Playground - Type a prompt, adjust temperature/topK/topP, generate a theme, see every M3 component update live
• Weather - 8 weather conditions, each auto-generating a contextual theme
• Test Harness - Matrix view: run prompts against multiple config presets, compare results
• Settings - Gemini Nano status, model download/warmup, manage cache

Running

1. Open in Android Studio
2. Select the sample run configuration
3. Run on a device or emulator

On-Device LLM

This sample uses Gemini Nano via ML Kit for on-device theme generation. Requires a supported device (Pixel 9+, Samsung S25+) with a locked bootloader. On unsupported devices, the app falls back to the default Material You theme.

For the cross-platform sample with cloud LLM support (OpenAI via Ktor), see the sample-shared module.