How this founder built a better Duolingo with Codex | William Imoh
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William Imoh is the founder of Hackmamba and the creator of Mural, an AI language tutor he built after a 1,000-day Duolingo streak still left him unable to hold a conversation in Norwegian. In this episode, he shows how he used Codex and GPT-Live to build native iOS and Android apps despite having no Swift or Kotlin experience, and explains how he designed Mural to teach through complete immersion. He also walks through the Lord of the Rings–themed team of Grok Bots that helps him run a 25-person company, from Gandalf as chief of staff to Legolas in marketing and Aragorn in sales.
Biggest takeaways:
- When agents write the code, the programming languages you know matter far less. William had never written Swift, but he wanted Mural to feel truly native, so Codex built it in Swift for iOS and Kotlin for Android. The technical stack followed the product vision, not the skills of the founder.
- Taste is often just design judgment expressed clearly. William told Codex to create a minimal, Apple-quality app that felt like autumn. When the first version came back in dark mode, he redirected it toward warm colors, gradients, and a lighter visual style.
- Product management experience translates directly into better prompting. William structures his requests as epics and user stories tied to specific user problems. That discipline gives the agent clearer goals and consistently produces stronger results.
- Real-time voice is finally good enough to build around, but it remains expensive. William says Mural would not have been possible without GPT-Live-1. A 30-minute session costs roughly $3 to $5, which is expensive for software but still cheaper than an on-demand human tutor.
- Agents feel more like colleagues when they have clear identities and jobs. William’s Grok Bot team includes Gandalf as chief of staff, Legolas in marketing, Elrond in engineering, and other Lord of the Rings characters across the business. The personas make each agent’s responsibilities easier to understand and delegate to.
- Useful context comes from access, not longer prompts. William connected his agents to Google Workspace, Linear, Notion, Pipedrive, QuickBooks, his calendar, and browser tools. He grants broad access by default, while keeping banking and customer data protected.
- The future may be custom systems of record with AI on top. William built Three Pipes, an internal HR tool that combines email, calendar, and meeting notes to track and rank candidates. Instead of adapting his workflow to generic software, he created the database his company actually needed.
- Better models reduce the need for elaborate skill libraries. Most of William’s skills became unnecessary as the underlying models improved. The few that survived encode durable expertise, including growth strategy, content strategy, and removing AI-style writing.
- When an agent stalls, restart with clearer instructions and add a reviewer. William begins a fresh session, breaks the task into steps, and asks the agent to inspect its own work. He also uses Grok Bot to review Cursor’s output.
Blog and detailed workflow walkthroughs from this episode:
William Imoh Built a Norwegian Tutor That Refuses to Speak English: https://www.chatprd.ai/how-i-ai/william-imoh-built-a-norwegian-tutor-that-refuses-to-speak-english
↳ Create an Immersive AI Language Tutor: https://www.chatprd.ai/how-i-ai/workflows/create-an-immersive-ai-language-tutor
↳ How to Manage Business Operations with Role-Based AI Agents: https://www.chatprd.ai/how-i-ai/workflows/how-to-manage-business-operations-with-role-based-ai-agents
↳ Build a Native Mobile App with AI and Clear Product Direction: https://www.chatprd.ai/how-i-ai/workflows/build-native-mobile-app-ai-product-direction
If you’re enjoying these episodes, reply and let me know what you’d love to learn more about: AI workflows, hiring, growth, product strategy—anything.
Catch you next week,
Lenny
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