I built a free coding game with 18,000 questions — can you predict the output?

Description and use

A free browser-based game was built to let developers predict code output from 18,000 questions across 18 languages and 6 stacks, featuring 5 difficulty levels and gamification.

Problem

Developers need an interactive way to practice predicting code output across many languages and difficulty levels.

Outcome

The game provides a large, diverse, and gamified environment for developers to practice code output prediction, with ongoing improvements based on user feedback.

Workflow

• 1. Designed game concept and question structure.
• 2. Used Gemini and Google AI Studio to generate code snippets and answer options.
• 3. Reviewed and refined questions to ensure clear, predictable answers.
• 4. Implemented browser-based interface with practice and challenge modes.
• 5. Added gamification elements: daily challenges, XP, streaks, leaderboards, achievements.
• 6. Released the game for free without installation.
• 7. Collected feedback from developers on correctness, difficulty, and language coverage.

Evidence

I recently launched OUTPUT? — Code Prediction Game, a free browser-based game that challenges developers to predict the output of real code snippets.

Source

Approximately 18,000 coding questions

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18 programming languages and 6 technology stacks

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5 difficulty levels

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I developed OUTPUT? as a solo creator using Gemini and Google AI Studio.

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One of the biggest challenges was ensuring that coding questions have clear, predictable answers.

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