How It Works

Real-time multiplayer Guess Who with a hybrid AI verification engine — deterministic lookups for facts, local VLM for vibes.

Game Flow

1Enter your name and get matched with another player via FIFO matchmaking.

2Both players see 24 randomly selected characters and secretly pick one as their identity.

3Take turns asking yes/no questions or guessing the opponent's character.

4Questions are evaluated against the opponent's secret character — factual traits resolve instantly, subjective ones go through the AI.

5Eliminate characters from your board based on answers. Your opponent sees eliminations in real time.

6Correctly guess the opponent's character to win!

Hybrid Verification Engine

When you ask a question, the system decides how to answer it:

Question: "Do they have brown hair?" │ ▼ ┌──────────────────────────────┐ │ Check character attributes │ │ (DB key/value lookup) │ └──────────────┬───────────────┘ │ Match found? ──YES──▶ Instant verdict │ NO │ ▼ ┌──────────────────────────────┐ │ Send to VLM (Ollama) │ │ image + attributes + question│ └──────────────┬───────────────┘ │ ▼ Yes / No / Inconclusive

Factual questions (hair color, glasses, hat) resolve instantly from the database.

Subjective questions ("looks friendly", "seems athletic") get evaluated by the AI model looking at the character's image and metadata.

If the model can't decide, you get Inconclusive — the round still completes normally.

Tech Stack

BackendScala 3 + ZIO

HTTP / WebSocketZIO-HTTP + Tapir

FrontendSvelteKit + TypeScript

DatabasePostgreSQL + Skunk

AI ModelOllama (qwen2.5vl:3b)

Proxy / TLSCaddy (auto HTTPS)

Architecture

┌──────────┐ WebSocket ┌──────────────┐ │ Browser │◀───────────▶│ ZIO-HTTP │ └──────────┘ │ (Game Loop) │ └──────┬───────┘ │ ┌────────────┼────────────┐ ▼ ▼ ▼ ┌──────────┐ ┌──────────┐ ┌──────────┐ │PostgreSQL │ │ Ollama │ │ Caddy │ │(chars, │ │ (VLM) │ │(TLS + │ │ history) │ │ │ │ static) │ └──────────┘ └──────────┘ └──────────┘

WebSocket — persistent connection for the entire game session
PostgreSQL — characters with flexible JSONB attributes + game history + Elo ratings
Ollama — local CPU inference for subjective question evaluation
Caddy — automatic HTTPS via Let's Encrypt

WebSocket Protocol

Tagged-union message protocol over WebSocket:

Client → Server

SelectCharacter — pick your secret character
SubmitQuestion — ask a yes/no question
GuessCharacter — guess opponent's character
EliminateCharacter — flip a card

Server → Client

GameStart — match found, 24 characters
TurnStart — whose turn it is
RoundResult — Yes / No / Inconclusive
GuessResult — correct or wrong
GameOver — winner + Elo delta

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