Game Mechanics

Flip game

Flip is the headline game on ThisOrThat. Buyer picks a card (or a multi-card cart), chooses a spread, and a coin flip decides whether they pay BELOW market or ABOVE. Either outcome, they get the card. The spread is the gambling element; the card delivery is the certainty.

The math

Every Flip listing has three numbers stored in FlipConfig:

cardValue — the card's market value (or lot total)
spread — typically 0.25 (25%, our current default)
winPrice = cardValue × (1 - spread) — what buyer pays on a WIN
losePrice = cardValue × (1 + spread) — what buyer pays on a LOSE

Example: $100 card at 25% spread:

Win → buyer pays $75 (saves $25)
Lose → buyer pays $125 (overpays $25)
Either way → card ships

The provably-fair flow

The buyer can verify the outcome wasn't rigged. Sequence:

Buyer commits the play with a Stripe payment intent (manual capture)
Server generates seed: crypto.getRandomValues(32 bytes)
Server hashes seed: sha256 = SHA-256(seedHex)
Server anchors hash on Solana (memo transaction). Buyer can verify the hash existed before the result was decided.
Server reveals seed + computes outcome: seed[31] % 2 === 0 ? WIN : LOSE (last byte's parity)
Buyer's UI animates the coin flip, lands on result
Server captures the right amount via Stripe: winPrice if win, losePrice if lose
Order created, label printable, fulfillment proceeds

✓ The trust model

The hash gets anchored on-chain BEFORE the seed is revealed. Anyone can verify after the fact: take the revealed seed, recompute SHA-256, check it matches what's anchored on Solana. If the hash doesn't match, the operator cheated. If it does, the math is verifiable.

Multi-card flip carts

Buyers can build a cart of 2+ cards and flip them all on one outcome. Use case: stacking sub-$15 cards over the shipping floor. Math is identical — cardValue becomes the cart total.

Cart	Total value	Spread	Win price	Lose price
1× $50 card	$50	25%	$37.50	$62.50
3× $5 cards	$15	25%	$11.25	$18.75
5× $20 cards	$100	25%	$75	$125

Eligibility rules

Solo flip floor: a single card needs marketValue ≥ $15 to be flipped on its own (shipping economics). Cards below are flagged flipEligible: false.
Cart total floor: a multi-card cart needs combined ≥ $15. The per-card flag is bypassed for cart length ≥ 2.
Pull-only cards: cards intentionally routed as Pull-only (pullEligible: true, flipEligible: false) can still be added to flip carts when combined with other cards.

Lots vs singles in Flip

A "lot" is a Listing with multiple cards stored as a single unit. The buyer flips the whole lot once, ship every card on the same outcome.

City lots, team lots, player lots — all valid Flip listings
The FlipConfig.cardValue is the lot's total_value
One outcome, one shipment, all cards together

Spread defaults

Currently 25% across the system (recently bumped from 15%). The spread number is the operator's risk knob:

Lower spread (10-15%) → buyers happier, smaller upside on losses, less margin per play
Higher spread (25-35%) → bigger swings, gambling appeal stronger, margin per loss-play larger
Above 40% → starts looking predatory, FTC risk

Code references

Game logic: thisorthat/src/lib/games/flip.ts
Play endpoint: thisorthat/src/app/api/play/flip/route.ts
Payment intent path: thisorthat/src/app/api/payment/route.ts
Solana anchoring: thisorthat/src/lib/blockchain/solana.ts
Settlement on Stripe: capture-or-cancel via webhook handlers in /api/stripe/webhook/route.ts

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