Develop browser games with Gemini 3 Pro Canvas | Alpha | PandaiTech

Develop browser games with Gemini 3 Pro Canvas

Step-by-step process of creating a Galaga-style game using Gemini 3 Pro's Canvas, asking for prompts, running the code, and iterating on features.

Learning Timeline
Key Insights

Using Thinking Models First

Do not ask the coding AI (Gemini) to brainstorm the game mechanics from scratch. Use a 'Thinking Model' first to generate a detailed functional spec, then feed that spec to Gemini for coding. This produces higher quality code.

The 'Fresh Chat' Rule

If a feature update breaks the UI (e.g., overlays blocking the game) and one follow-up prompt doesn't fix it, abandon the chat. Starting a fresh chat with the consolidated requirements is often faster than debugging via chat.

Phantom API Requests

Gemini may occasionally hallucinate a requirement for an API key when code errors occur. If the game logic shouldn't require external data, this is a bug—restart the prompt rather than trying to provide a key.
Prompts

Meta-Prompt for Game Description

Target: ChatGPT / Thinking Model
I want to make the classic game Galaga. Give me a prompt for that. Don't include any specific tech.
Step by Step

Generating the Game Code

  1. Open a separate 'Thinking Model' AI (e.g., ChatGPT o1 or similar) to prepare your prompt context.
  2. Input a request for a non-technical description of the desired game (see Prompt card).
  3. Copy the detailed description generated by the Thinking Model.
  4. Navigate to the Gemini interface.
  5. Ensure the code execution/Canvas toggle is set to 'ON' (usually located near the input field or settings) to enable interactive previews.
  6. Paste the detailed description into the Gemini prompt field.
  7. Submit the prompt and wait for Gemini to generate the HTML/JS code.
  8. View the interactive preview window that appears automatically to test basic functionality (e.g., movement, scoring).

Iterating and Debugging Features

  1. Type a request for a specific new feature (e.g., 'Add a status bar at the bottom') into the chat input.
  2. Wait for Gemini to update the code block and refresh the preview.
  3. Test the new feature in the preview window.
  4. If the UI glitches or the code breaks the layout: Do not attempt to prompt-fix multiple times.
  5. Open a 'New Chat' immediately.
  6. Paste the original prompt plus the new feature request into the new chat to generate a clean version of the code.

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