Demo: One-Shotting a Flappy Bird iPhone App with Devin and Fable 5.1

Melvin Vivas · X video post · 2026-09-18 · 0:12 · 526 views · Open on X

Topics: AI Dev Tools & Productivity, AI Agents, Tool Use & MCP · Level: beginner

Summary

A 12-second silent demo in which Melvin Vivas builds a Flappy Bird iPhone app with the AI coding agent Devin from one prompt ("one-shotted"). He used Fable 5.1 and Devin's new macOS environment, which he says works well for iOS development. The post shows a result, not a tutorial, so there are no steps or prompts to copy.

Key points

• Devin (by Cognition) is an autonomous AI coding agent. Here it built a working Flappy Bird iPhone app from a single prompt.
• The creator says he used 'Fable 5.1' for this run. The post doesn't say what Fable 5.1 is; it may be a model or version option inside Devin.
• Devin now has a macOS environment. iOS apps need macOS and Xcode to build, so this lets the agent build and run iPhone apps itself.
• The creator says the new macOS environment is 'really great for iOS development'.
• A small, well-known game like Flappy Bird is a quick way to test what an agent can build from one prompt.
• The video has no speech and shows no prompt, settings or code. It is a showcase, not a step-by-step guide.

Resources mentioned

• Devin · tool · x.com · paid
  A desktop app from the makers of the Devin coding agent for planning, delegating, reviewing and shipping work across fleets of local and cloud coding agents.
  Also in: Using the Devin iOS App to Build iOS Apps (Quick Demo) (Melvin Vivas on X · notes), Use Your ChatGPT Plus/Pro Subscription to Run Devin (Melvin Vivas on X · notes), OpenAI DevDay recap: Dots, GPT-6.1 Sol, Codex Cloud, Agents API (Melvin Vivas on X · notes), Devin price cuts and top score on FrontierCode 1.1 Extended (Melvin Vivas on X · notes) and 44 more
• Fable · tool · anthropic.com · paid
  Named as what the creator used with Devin for this build; the post gives no details about what it is.
  Also in: Subagents with mixed models: a strong planner and a fast executor (Melvin Vivas on X · notes), Cognition's SWE-2 Coding Model Now in Devin (Melvin Vivas on X · notes), GPT-6 Astra Access Across Plans vs Fable on Claude Max (Melvin Vivas on X · notes), Cutting AI Coding Costs by Routing Most Work to Commodity Models (Melvin Vivas on X · notes) and 10 more

Try this

• Use an AI coding agent such as Devin, running in a macOS environment, to build a simple iPhone game like a Flappy Bird clone from a single prompt.