Ampai

Ampai is a mahjong score tracking and sharing app. Incorporated in 2023, it has grown to approximately 12,000 users and has been adopted as the official scoring system for the Japan Professional Mahjong League, including their international tournament “World Mahjong 2025.”

I served as co-founder, handling technical direction, frontend development, and product planning — alongside back-office responsibilities in the early days.

The frontend (Next.js), backend (Laravel), OG image generator (Node.js), and data stores (PostgreSQL / S3) are loosely coupled, so the same system serves both casual games among friends and professional league operations.

A common failure mode in mahjong score apps is losing track of the current state. Between complex rules and multi-step input flows, users need to know where they are, what has already been entered, and what comes next. Ampai addresses this at the screen level by making the next action explicit in each view.

The group management UI takes its cue from LINE group chats: a familiar space where friends can manage scores together. New members can join from a QR code without creating an account first, reducing setup work before a game starts.

Each member in the leaderboard appears with their icon or photo. Showing faces instead of only names makes the ranking easier to read at a glance and gives each score change a clearer social context.

Rule configuration is where first-time users often abandon mahjong apps. Ampai ships with templates for major rulesets including M.League, so a group can start with a known configuration and adjust only when needed. Advanced players can still override detailed settings without making the default path heavier.

The same product that handles casual games among friends also powers professional league operations. Infrastructure is managed as code with Docker and Terraform on AWS, with Cloudflare handling performance and security. PWA support delivers an app-like install experience without requiring an App Store submission.

Match results generate a dynamic OG image that players can share directly to X (Twitter) and other platforms. Making results easy to post gave the product a practical acquisition channel: shared score images introduced the app to new players through the context of an actual game.