# 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 on mobile, wider on sm+; condensed bold black numbers on white,
  purple empty-cell background by default — Excel Standard Purple `#7030A0`).
- **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.
- **Visual rhythm (soft)**: the generator avoids rows with 3 consecutive
  filled columns whenever possible (rejection-sampled per card). Hard
  invariants (5 per row + 5 per col) always win if the constraint can't
  be satisfied.
- **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 (light-blue ring and cream fill when
  called, dim when 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 5 fieldsets:
  - Giao diện: theme switcher (auto / light / dark; auto mirrors OS pref)
  - Chế độ quản trò: toggle to show MasterPanel on `/`
  - Tự động xổ: enable auto-call; speed slider (1–10 seconds)
  - Âm thanh: voice toggles for master + player + Vietnamese voice picker
    (every `vi-*` edge-tts voice; default Hoài Mỹ)
  - Màu ô trống: color picker + 10 Excel preset swatches
  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 3 with Svelte 5 (runes mode)
- **Runtime**: Svelte 5 runes ($state, $derived, $effect, $props)
- **Styling**: Tailwind CSS 4 (utility-first, animations)
- **Persistence**: localStorage (no backend)
- **Audio**: pre-generated MP3 clips bundled under `static/audio/{voiceId}/`. Built once by `scripts/generate-audio.py` using free `edge-tts` (Microsoft Neural). Runtime plays via plain HTML5 Audio — no TTS API at runtime.
- **Deploy**: GitHub Pages at `/loto` (canonical, via GitHub Actions)
- **Dev Profile**: code-server compatible via `/absproxy/{port}` basePath + HMR proxy config

## Architecture Overview

Single page (`/`):
- Always renders the player card (generate, mark, bingo popup, "Chờ N" toasts).
- When `settings.masterMode === true`, mounts MasterPanel below the player card — host controls, draw history, and the host's own player card.

State is entirely client-side. Each card / panel instance uses a unique localStorage prefix (`"loto"` for the player card, `"loto_master"` for host draw state, `"loto_master_card"` for the host's own card).

## Deployment

- **Production**: GitHub Pages at `https://tiennm99.github.io/loto/` (canonical, basePath `/loto`). Deployed by the `deploy-pages` job in `.github/workflows/ci.yml` on push to `main`.
- **Development**: `npm run dev` (local), `npm run dev:codeserver` (code-server via proxy).
- **Build**: `npm run build:gh` generates static export to `build/` directory with the `/loto` basePath.

## Key Acceptance Criteria

- [x] Player card is 9×9 with **exactly 5 per row and 5 per column**.
- [x] Numbers within each column are **ascending top-to-bottom**.
- [x] Player can click cells to toggle crossed state.
- [x] Player can clear all marks on the current card without regenerating it (confirm prompt when marks exist).
- [x] No row has 3 consecutive filled columns (soft constraint, rejection-sampled).
- [x] Master speaks the called number aloud in Vietnamese (bundled MP3, no runtime TTS API).
- [x] Player hears "Chờ N" when a row is one away and "Kinh" on bingo.
- [x] Voice picker in settings — switch among every Vietnamese edge-tts voice.
- [x] Player numbers comfortably readable on a 360 px viewport.
- [x] Cell tap on mobile gives haptic + active-press + animated cross-out feedback.
- [x] Master "Số vừa xổ" hero is the page focal point and auto-scrolls into view on each draw.
- [x] Cold first paint shows a faded preview card + welcome line, not a gray placeholder.
- [x] Bingo celebration tiers: 3rd+ row triggers a CSS confetti rain on top of the popup.
- [x] Bingo popup triggers when row is complete, shows row number and "Kinh!" message.
- [x] Player may keep marking after a Kinh — no game-end lock.
- [x] Toast notifications show "Chờ X" before bingo (one number remaining).
- [x] Host can draw numbers and see them on the **11×9 last-digit-aligned master board**.
- [x] Master board shows **draw order** on each called cell for Kinh verification.
- [x] Host has their own player card (isolated by localStorage prefix).
- [x] Offline persistence via localStorage (grid and crossed state).
- [x] Dark mode support (Tailwind dark classes).
- [x] Mobile-responsive (base + sm breakpoints).
- [x] HMR works on code-server via proxy.
- [x] Player card rendered as 3 stacked Tân Tân mini-cards with separator labels.
- [x] Settings modal with 4 fieldsets (theme, master mode, auto-call, color); applies to both grids; persisted.
- [x] Theme switcher (auto / light / dark) with explicit dark class selector on `<html>`.
- [x] Master mode toggle to show MasterPanel on player page.
- [x] Auto-call timer (1–10s speed) with start/stop button.
- [x] Mobile-responsive layout (aspect-square sm:aspect-[3/5] cells, text scaling).
- [x] MasterPanel extracted; mounted conditionally on `/` when master mode is on.
- [x] PageFooter with tagline + link.

## Visual Language

- **Wordmark gradient**: rose → amber → rose, italic + drop-shadow — vintage carnival marquee feel.
- **Player accent**: indigo → purple (primary brand, positive action).
- **Host accent**: orange (subordinate to wordmark; not gradient).
- **Completed rows**: sky blue (success indicator).
- **Waiting toast**: amber (attention, ephemeral).
- **Emojis**: 🎉 ✨ 🎊 🥳 ❤️ (celebration, joy). Confetti rain on 3rd+ bingo per card.
- **Haptic**: 10 ms vibration on cell tap (mobile only, where supported).

## 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: 2026-05-09 (scope locked: Lô tô hội chợ Tân Tân + theme/master/auto-call)
Last synced: 2026-05-09 (deploy target switched to GitHub Pages)