Learn how I managed context to keep Copilot focused, used the Plan agent to sharpen vague requirements, and more.

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Building a countdown app with GitHub Copilot reveals practical patterns for AI-assisted development. Key lessons include managing context windows by starting fresh chat sessions when old context becomes irrelevant, using the Plan agent to clarify vague requirements through targeted questions that reveal edge cases, and applying test-driven development to catch bugs before deployment. Custom agents like a UI Performance Specialist provide specialized expertise for specific tasks. The iterative development process embraced failures as learning opportunities, including a world map that rendered incorrectly but highlighted the importance of providing sufficient context. The project evolved from a basic countdown to include timezone support, intensity-based fireworks, and multiple themes, demonstrating how to scope ambitiously while implementing incrementally.

Context windows, Plan agent, and TDD: What I learned building a countdown app with GitHub Copilot

The community suggestion that steered our course

Plan agent: The questions I hadn’t thought to ask

Context window management: Just keep what you need

Implementation: Modular, test-driven, and that map

Fireworks: Building anticipation toward midnight