LINEだけで完結する飲み会アプリ｜まるっと飲み会くん

App Introduction Page: https://nomikai-app.com

An app for scheduling drinking parties and splitting bills within LINE. Once you add the friend, you proceed from the card that arrives in the chat.

What the organizer does

• Select members and candidate dates, then press "Create and notify" once
• View the collected responses and confirm the schedule
• Enter the accounting, and the bill-splitting results appear as a card

What participants do

• Open the card that arrives and select "Going / Keep / Not going" for each candidate date
• From the settlement card, proceed directly to the PayPay transfer screen

Other features

• If advances are crossed between the first and second drinking parties, they cancel each other out to reduce the number of transfers
• People who haven't responded and those who haven't paid automatically receive reminders
• You can search for restaurants within LINE. You can choose from other members' favorites or propose a restaurant yourself
• You can also use just the bill-splitting calculation without doing schedule adjustment

Technology Stack

• Framework: Next.js 15 (App Router) / React 19 / TypeScript
• Hosting: Vercel (Scheduled tasks like reminders for unanswered and unpaid users use Vercel Cron)
• UI: Tailwind CSS / lucide-react (icons) / react-virtuoso (list virtualization) / @dnd-kit (settlement card reordering)
• LINE: Messaging API (direct calls) + LIFF (@line/liff). Login via LINE account
• Authentication: JWT (jsonwebtoken)
• Database: Supabase (PostgreSQL) + Row Level Security. Direct access via node-postgres
• Encryption: PayPay IDs stored with AES-256-GCM
• External APIs: Google Places + Tabelog Gourmet (restaurant search), PayPay (transfers)
• Error monitoring: Sentry
• Testing: Vitest (unit) + Playwright (E2E)

It's free and doesn't require app installation. Participants only need to add the friend once at the beginning.