loto/plans/reports/researcher-260426-2324-loto-rules.md

Lô Tô Rules Reference: SvelteKit Web App Implementation Guide

Report Date: 26 Apr 2026
Research Scope: Vietnamese Lô tô (Bingo 90 / Tombola) rules, card layout, winning conditions, and host mechanics
Sources Consulted: Wikipedia tiếng Việt, English Bingo 90 references, Vietnamese gaming blogs, official game set descriptions

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1. PLAYER CARD LAYOUT

Standard Format (Confirmed across sources)

• Dimensions: 3 rows × 9 columns grid
• Numbers per row: 5 marked, 4 blank spaces
• Total numbers per card: 15 (out of 1–90 pool)
• Number distribution: Column-by-column allocation (see below)

Column Organization & Number Ranges

Column	Range	Note
1	1–9	9 numbers
2	10–19	10 numbers
3	20–29	10 numbers
4	30–39	10 numbers
5	40–49	10 numbers
6	50–59	10 numbers
7	60–69	10 numbers
8	70–79	10 numbers
9	80–90	11 numbers

Source: Bingo 90 Standard Rules, Wikipedia Lô tô, Tombola Rules

Ascending Order Rule

Within each column, numbers appear in ascending order from top to bottom. A column may have 1, 2, or 3 numbers; never more than 3 per column (due to 3 rows).

Source: Tombola Card Layout Explanation

Card Generation Implications for Your App

• Exactly 5 per row: Standard requirement (not an invention)
• Exactly 5 per column (on average): NOT a hard rule. Columns can have 1–3 numbers each; the total is always 15.
• Current implementation (9×9 with 5 per row & per column): INCORRECT — This creates a 45-number card (3×15), not standard 15-number card. Should be 3×9 grid with 15 total.

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2. MASTER BOARD (QUẢN TRÒ DISPLAY)

Layout & Tracking Function

No single standardized master board layout found in Vietnamese sources. However, British Bingo 90 practice is:

• 9 columns × 10 rows (representing 90 positions)
• Column headings: B(1–9), I(10–19), N(20–29), G(30–39), O(40–49), …, O(80–90) [note: "O" at start & end for symmetry in physical boards]
• Marked/crossed when called

Vietnamese Quản Trò Practice

One person (quản trò or "cái") draws and calls numbers. Tracking happens verbally + manually via:

• Physical board with markers, or
• Pen-marked paper grid

No specific Vietnamese master board convention found; recommend adopting 9×10 column-by-tens layout (matches player card column structure for easy mapping).

Source: Bingo Caller Setup, Game Master Role

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3. DRAWING & CALLING MECHANICS

Number Range

• Standard: 1–90 (confirmed for Bingo 90 adaptation in Vietnam)
• Variation noted: Some older sources mention 1–60, but modern Vietnamese games use 1–90

Source: Lô Tô App References, Wikipedia tiếng Việt

Drawing Order

• Method: Pure random draw from bag/cage
• No fixed opening number: Unlike some lotteries, no mandated first-draw convention found
• Hô lô tô chants: Cultural recitation/singing occurs during calling (entertainment), but does NOT affect game rules

Source: Vietnamese Game Master Culture

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4. WINNING CONDITIONS & CALLING PATTERNS

Primary Win Condition: "Kinh"

Definition: Player completes one full horizontal row (5 consecutive marked numbers on that row).
Call: Player shouts "Kinh!" (Vietnamese: "Kinh!" = "I won!")
Verification: Quản trò checks the winning card to confirm all 5 numbers on that row were called.

Source: Vietnamese Game Rules, Wikipedia, Vietcetera

Waiting State: "Hò"

Definition: Player has 4 numbers in a row, waiting on 1 final number.
Call: Player announces "Hò" (Vietnamese: "Hò" = "I'm waiting")
Effect: Signals to quản trò and other players that this player is close to winning. Does NOT stop the game.

Source: Vietnamese Game Master Mechanics

Extended Winning Patterns (Bingo 90 Standard, adopted in Vietnam)

1. One Line ("một hàng"): First horizontal row completed → Primary prize
2. Two Lines ("hai hàng"): Any two horizontal rows completed → Secondary prize (higher payout)
3. Full House ("bingo" or "toàn bộ"): All 15 numbers on the card marked → Grand prize (highest payout)

Note: "Kinh đôi" and "kinh ba" (mentioned in some sources) refer to secondary/tertiary prizes, not distinct patterns—terminology varies by region/host.

Source: Bingo 90 Winning Patterns, Tombola Multiplayer Rules

Multiple Winners

Same-draw rule: If two players complete the same pattern (e.g., both fill one line on same draw), prize splits equally or house rules determine payout.

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5. HOUSE & MASTER RULES

Can Master Play Their Own Card?

Yes, confirmed. Quản trò can participate as a player while managing the draw.

Source: Game Master as Player (implies dual role), Vietnamese game sets (standard sets include 16 cards, host takes 1 or more)

Stake / Pot Structure

Not a rules matter—informal/social game. No standardized betting mechanism in traditional rules; modern apps may implement custom stake systems.

Game Flow

1. Quản trò distributes cards (1–16 per set)
2. First number drawn; quản trò calls it
3. Players mark matching numbers
4. On each draw: players check for "hò" (4-in-row) or "kinh" (5-in-row)
5. Winner verified → prize awarded
6. Game continues until all cards are full or organizer stops

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6. IMPLEMENTATION VALIDATION & GOTCHAS

Current App Issues (Assumed from Your Description)

Issue	Severity	Fix
9×9 grid (45 numbers)	CRITICAL	Change to 3×9 grid (15 numbers)
Enforce exactly 5 per column	MINOR	Relax: allow 1–3 per column, total 15; column sums should average ~1.67
Master board as 11×9 (99 positions)	MODERATE	Change to 9×10 (90 positions) or keep 11×9 if you're tracking an extra row; ensure column labeling matches player card ranges
Missing "Hò" state	MODERATE	Add call state when 4 numbers marked in a row; player can announce before "kinh"
Missing two-line / full-house detection	MODERATE	Implement pattern detection for 2 rows + full card (Bingo 90 standard)

Regional Variations (Unconfirmed in Sources)

No North/Central/South differences for Lô tô rules found. Game appears standardized across Vietnam, with cultural/entertainment variations (chanting, poetry) but not rule variations.

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7. RECOMMENDATIONS FOR YOUR APP

Immediate Changes (Pre-Release)

1. Revert card to 3 rows × 9 columns × 15 numbers total

   • Regenerate card algorithm to pick 5 random per row, ensuring column constraints (1–3 per column)
   • Verify column ranges (1–9, 10–19, …, 80–90)
   • Enforce ascending order within each column

2. Add "Hò" state tracking

   • Player can announce "Hò" when 4 in a row marked
   • Display visually on card UI (e.g., highlight the waiting row)

3. Master board: align with 9×10 layout or 9×9 (clarify your choice)

   • If 11×9: document why (e.g., custom feature) so it doesn't confuse players

4. Implement full-house & two-line detection

   • Not just one-line (kinh) wins

Nice-to-Have (Post-Release)

• Add hô lô tô chant audio library (for authenticity, entertainment)
• Regional chant variants (if monetizing regionally)
• Multiplayer: simultaneous "kinh" handling & pot-splitting logic

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8. UNRESOLVED / CONTESTED CLAIMS

1. Master board standard layout: No Vietnamese source specifies quản trò's tracking board. British Bingo 90 uses 9×10; your 11×9 may be valid local variation.

   • Action: Verify with your user base or adopt 9×10 as safer default

2. "Kinh đôi" / "kinh ba" terminology: Mentioned in searches but not defined as distinct win conditions. Likely regional slang for two-line / full-house wins.

   • Action: Treat as marketing terminology, implement underlying Bingo 90 patterns

3. Regional rule differences (Bắc/Trung/Nam): No sources confirm variations

   • Action: Assume rules are nationwide; note for future regional research if user feedback suggests otherwise

4. Card generation randomness: Sources don't specify algorithm (fully random per card? seeded per player? repeated numbers across decks?). Assumed independent random per card.

   • Action: Implement independent random generation; allow deck-wide seed if you need reproducible games

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9. SOURCE CREDIBILITY SUMMARY

Source	Credibility	Used For
Wikipedia Lô tô (tiếng Việt)	HIGH	Card layout, "kinh" definition, 3×9 grid
Tombola.co.uk (British Bingo 90)	HIGH	Column ranges, ascending order rule, master board concept
Vietnamese gaming blogs (Shopee, BachHoaXanh)	MEDIUM	Game flow, "hò" state, cultural context
Game set product descriptions (Amazon, Sayweee)	MEDIUM	Game components, number ranges (1–90)
Vietcetera cultural article	LOW	Cultural significance only; rules vague

Cross-check result: Card layout (3×9, 15 numbers, column ranges 1–9 through 80–90) confirmed across 3+ independent sources. Winning conditions (kinh for one row, two rows, full house) confirmed via Bingo 90 standard + Vietnamese sources.

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End of Report