loto/docs/project-overview-pdr.md

Lô Tô — Project Overview & PDR

What is Lô Tô?

This app replicates Lô tô hội chợ (Vietnamese fairground / carnival lô tô), specifically the Tân Tân style most familiar from southern Vietnam class reunions and Tết gatherings. Inspiration: TN1 class reunions (2014–2017) where players ran build of physical bingo cards.

It is not the British Bingo 90 / Italian Tombola 3×9 / 15-number ticket. That format is intentionally out of scope.

Game Variant & Scope

In scope (Lô tô hội chợ Tân Tân)

• Card: 9 rows × 9 columns. Exactly 5 numbers per row AND exactly 5 numbers per column (45 numbers per card; 36 blanks).
• Visual layout: card displayed as 3 stacked 3×9 mini-cards with traditional separator labels — Tân Tân, An khang thịnh vượng, Tân Tân tốt nhất — matching the physical Tân Tân BAMBOORAFT paper sheet (tall non-square cells, condensed bold black numbers on white, blue empty-cell background by default).
• Column ranges: col 0 = 1–9, col 1 = 10–19, …, col 7 = 70–79, col 8 = 80–90.
• Within a column: numbers placed top-to-bottom in ascending order.
• Number pool: 1–90.
• Win condition: 1 row complete = "Kinh!". After winning, the player may keep playing further rows (game does not end).
• Waiting state: when a row needs only 1 number, app announces "Chờ N".
• Host (quản trò) draws numbers from a shuffled 1–90 deck, tracks them on a master board with circular tokens (pink ring for 1–49, green for 50–90, cream fill on called, dim on uncalled, red ring + scale on the most recent draw), and may also play their own card.
• Settings: gear icon in headers opens a modal with a color picker for the empty/blank cell color (default brown matches physical card). Persisted to loto_settings.

Out of scope

• 3×9 / 15-number Bingo 90 / Tombola tickets (European format).
• Two-line and full-house win tiers.
• Custom number ranges (1–75 American bingo, etc.).
• Stake / pot / payout logic.
• Multiplayer real-time sync.

Core Mechanics

• Players: Generate a randomized 9×9 card. The generator guarantees 5 per row and 5 per column (constraint-aware picker, not loose weighted random). Numbers within each column ascend top-to-bottom. Click cells to mark them.
• Host: Draws numbers randomly from a shuffled 1–90 deck, shows the current number, and tracks all called numbers on an 11×9 master board aligned by ones-digit (col 0 = 1–9, col 8 = 80–90; 1 / 11 / 21 / … / 81 share row 1, etc.). Each called cell shows its 1-based draw order as a small superscript so the host can quickly verify a "Kinh!" claim by reading the order across the winning row.
• Bingo: When a row is complete, a celebration popup shows "Kinh!" with confetti. Player keeps playing afterward — no game-end gate.
• Waiting: "Chờ N" toast when a row is one number away.

Tech Stack

• Framework: SvelteKit 2 with Svelte 5 (runes mode)
• Runtime: Svelte 5 runes ($state, $derived, $effect, $props)
• Styling: Tailwind CSS 4 (utility-first, animations)
• Persistence: localStorage (no backend)
• Deploy: Cloudflare Pages (root domain), GitHub Pages fallback (/loto)
• Dev Profile: code-server compatible via /absproxy/{port} basePath + HMR proxy config

Architecture Overview

Two public pages:

1. / — Player page. Generate a card, click cells to mark them, see bingo popup and waiting toasts.
2. /master — Host page. Control number drawing, view 9×10 master board (tracking called vs uncalled), and host's own player card.

State is entirely client-side. Each page/card instance uses a unique localStorage prefix (e.g., "loto" for player, "loto_master" for host's state, "loto_master_card" for host's player card).

Deployment

• Production: Cloudflare Pages at loto.miti99.com (canonical, CF dashboard, root basePath). GitHub Pages serves only a redirect to the canonical URL via .github/workflows/deploy-github-pages.yml.
• Development: npm run dev (local), npm run dev:codeserver (code-server via proxy).
• Build: npm run build generates static export to build/ directory.

Key Acceptance Criteria

• Player card is 9×9 with exactly 5 per row and 5 per column.
• Numbers within each column are ascending top-to-bottom.
• Player can click cells to toggle crossed state.
• Bingo popup triggers when row is complete, shows row number and "Kinh!" message.
• Player may keep marking after a Kinh — no game-end lock.
• Toast notifications show "Chờ X" before bingo (one number remaining).
• Host can draw numbers and see them on the 11×9 last-digit-aligned master board.
• Master board shows draw order on each called cell for Kinh verification.
• Host has their own player card (isolated by localStorage prefix).
• Offline persistence via localStorage (grid and crossed state).
• Dark mode support (Tailwind dark classes).
• Mobile-responsive (base + sm breakpoints).
• HMR works on code-server via proxy.
• Player card rendered as 3 stacked Tân Tân mini-cards with separator labels.
• Settings modal with empty-cell color picker; applies to both player and master grids; persisted.

Visual Language

• Player gradient: indigo → purple (primary brand, positive action).
• Host gradient: orange → red (higher-stakes, control action).
• Completed rows: emerald (success indicator).
• Waiting toast: amber (attention, ephemeral).
• Emojis: 🎉 ✨ 🎊 🥳 ❤️ (celebration, joy).

Future Considerations (Not Committed)

• Undo last crossed cell
• Sound effects on bingo
• Theme switcher
• PWA install
• Multiplayer sync (real-time via WebSocket)
• i18n beyond Vietnamese

Last reviewed: 2026-04-26 (scope locked: Lô tô hội chợ Tân Tân)