Google Generative AI Capstone Blog

"80% of indie game developers struggle with NPC diversity... and players notice."

🧠 The Problem: Flat NPCs Ruin Immersion

Creating compelling NPCs is a time-consuming task, especially for small teams or solo developers. Most games suffer from:

😴 Repetitive Characters: Same archetypes reused across worlds
⚖️ Unbalanced Stats: Leads to broken or unfair gameplay
📜 Weak Backstories: Generic or cliché lore that breaks immersion

🚀 Our Solution: NPC Genie

NPC Genie is an AI-powered toolkit that lets game devs instantly generate diverse, lore-rich, and stat-balanced characters with minimal input.

All you need to do is describe your game world, and we’ll give you:

🧬 2-3 Sentence Backstories
⚔️ Balanced RPG Stats (in JSON)
💬 Signature Dialogue Styles
🔍 RAG-based Similarity Search (WIP)

⚙️ Tech Stack

🧠 Google GenAI (Gemini 2.0 Flash)
🧱 LangChain + Pydantic
🧰 FAISS for similarity search
🔐 Kaggle Secrets + Python for API calls

📦 Step 1: Install Dependencies

!pip uninstall -qqy kfp
!pip install -qU "google-genai==1.7.0" "langchain" "pydantic" "faiss-cpu" "python-dotenv" "pandas" "langchain-core" "langchain-google-genai" "langchain_community"

🔐 Step 2: Setup API Key (Kaggle)

from kaggle_secrets import UserSecretsClient
GOOGLE_API_KEY = UserSecretsClient().get_secret("GOOGLE_API_KEY")

🧙 Step 3: Generate NPCs with Gemini

🧪 Few-Shot Prompting

We use a few-shot system to teach Gemini how good characters look:

few_shot_examples = """
Game World: Steampunk Metropolis

NPC 1:
- Name: Viktoria Gearspark
- Race: Human (Cyborg)
- Role: Inventor
- Stats: {"int":18, "dex":14}
- Backstory: "Lost her legs in an airship accident, now builds prosthetics for the poor."
- Dialogue: Technical but compassionate
- Secret: "Actually designs weapons for the underground resistance."
"""

🎯 Output Enforcement via Pydantic

from pydantic import BaseModel, Field
from typing import List, Dict

class NPC(BaseModel):
    name: str
    race: str
    role: str
    stats: Dict[str, int]
    backstory: str
    dialogue_style: str
    secret: str

class NPCList(BaseModel):
    npcs: List[NPC]

🧪 Structured Prompt + Error Handling

def generate_npcs(world_description: str, npc_count: int = 3) -> NPCList:
    prompt = f"""
    You are an RPG character generator.

    Generate {npc_count} NPCs for the game world:
    "{world_description}"

    Output structured JSON with fields: name, race, role, stats (1-20), backstory, dialogue_style, secret.

    Examples:
    {few_shot_examples}
    """

    response = model.generate_content(prompt)
    cleaned_text = re.sub(r"^```json\s*|```$", "", response.text.strip(), flags=re.MULTILINE).strip()
    parsed_json = json.loads(cleaned_text)

    try:
        return NPCList(**parsed_json)
    except ValidationError:
        print("🛑 Invalid NPC data! Retrying...")
        return generate_npcs(world_description, npc_count)

💡 Example Use Case

world_desc = "Cyberpunk slum with hacker clans"
npc_count = 3
npcs = generate_npcs(world_desc, npc_count)

Output (sample):

{
  "npcs": [
    {
      "name": "Echo Burn",
      "race": "Modified Human",
      "role": "Signal Sniper",
      "stats": {"dex": 17, "int": 15},
      "backstory": "Former radio DJ turned sniper after the towers fell.",
      "dialogue_style": "Sarcastic, poetic",
      "secret": "Still broadcasts secret messages to rebels."
    },
    ...
  ]
}

🖼️ Bonus: Portrait Generation

Using image prompts from the generated traits, we feed Gemini’s image model to create stylized NPC art:

def generate_npc_portrait(npc: NPC):
    contents = f"""
    Create a 4K fantasy portrait for this character:

    - Name: {npc.name}
    - Race: {npc.race}
    - Role: {npc.role}
    - Dialogue Style: {npc.dialogue_style}
    - Secret (hint only): {npc.secret[:50]}...
    """

⚖️ Limitations

While NPC Genie saves hours of manual work, there are some known issues:

🔁 Hallucinations: Rarely returns non-JSON or invalid characters

📊 Stat Inconsistency: Slight imbalance in stat distribution over many runs

🧠 World Consistency: Gemini sometimes mixes genres if world prompt is vague

🔮 Future Possibilities

We’ve already explored RAG-powered lore embedding and NPC similarity search — but there’s still so much more to build:

🧩 Multi-turn Character Refinement
🧠 Interactive World Expansion
🎮 Game Engine Integration
🌐 Collaborative NPC Worlds

👤 Author & Resources

Seif Khaled
AI enthusiast & software engineer passionate about blending storytelling with tech.

🎮✨ NPC Genie: AI-Powered Character Generator for Game Devs

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