# Debug a camera game through an MCP server inside the running app

PaperChase agent use case (free feed entry), version 1.0. Source: [u/vkorost on r/ClaudeAI](https://www.reddit.com/r/ClaudeAI/comments/1xeqtp1/i_built_a_laser_dryfire_shooting_game_with_claude/), 2026-10-25.

## What they did

The builder made a desktop game where a webcam pointed at the monitor detects laser hits, using on-screen markers so the camera can sit off to the side. It has 9 drills, 15 target figures and a two-player mode. To fix detection bugs, they put an MCP server inside the app so Claude could pull a camera frame, read the detector's numbers including the spots it rejected, check coordinates and send key presses.

## Worth knowing

The key design choice was that the MCP tools return raw measurements, not verdicts like 'hit detected', so the agent reasons from evidence instead of trusting a summary. The author says that cut a typical diagnosis from hours to about 90 seconds. The same pattern applies to any app with sensors or a camera in the loop.

## Workflow template

```text
Add a small MCP server inside your running app, not a separate process
Expose read tools for raw inputs (a camera frame, sensor values) and intermediate math, including rejected candidates
Add one write tool for simulated input, such as key presses
Ask the agent to reproduce the bug, then reason from the numbers it pulled before changing code
```

## Steps

1. **Read what they did.** Skim the source post linked below, then the summary on this page.
2. **Fill in the template.** Copy the prompt and replace every [bracketed] value with your own project details.
3. **Run it once and check.** Run it on a small task first and confirm the result yourself before you trust it on real work.

## Credit

Workflow reported by u/vkorost on r/ClaudeAI: https://www.reddit.com/r/ClaudeAI/comments/1xeqtp1/i_built_a_laser_dryfire_shooting_game_with_claude/
Related: https://github.com/vkorost/screenplink

Summary and template written by PaperChaseWebb in our own words. Questions: mgmt@paperchasewebb.com