HI-LO

Guess whether the next card lands above or below 8, build a multiplier with every correct call, and cash out before you're wrong. A pure nerve game, fully onchain.

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How it works

Overtime Hi-Lo is a streak game played against a fixed reference point: the card 8.

1. You place a bet and make your first guess in one transaction - Above or Below

2. The contract requests a random word from Chainlink VRF and draws a card from a 52-card deck

3. If the card's rank is on the side you guessed, your running multiplier grows. If it's wrong, you lose the bet. If it's exactly an 8, it's a push - multiplier unchanged, the run continues

4. After a correct guess, you choose again: guess once more to grow the multiplier, or cash out to take bet × current multiplier

5. You can keep going until you hit the multiplier cap or guess wrong

The comparison point is always the same. This is not a "higher or lower than the last card" game - every guess is measured against rank 8. The deck splits cleanly: ranks 2 through 7 are below, ranks 9 through Ace are above, and 8 itself is the push. Six ranks each direction means a 6 in 13 chance your guess is correct on any given card.

Cards are drawn fresh each round from the full 52 - there's no card-counting edge, because the deck doesn't deplete.

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The multiplier

Every correct guess multiplies your running total by a fixed factor:

factor = (12 − 13 × houseEdge) / 6

At the default 2% house edge, that's about 1.9567× per correct guess. The factor is constant - it doesn't change based on which card showed or how long your streak is. Five correct guesses in a row compounds to roughly 1.9567⁵ ≈ 28.6×, which is why the default multiplier cap sits at 25×.

The house edge is configurable within a hard-coded band of 2% to 5%. You can read the live value (houseEdgeE18) and compute the exact per-guess factor before you play.

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Cashing out

This is the heart of the game. After any correct guess, your accumulated multiplier is locked in as long as you stop. The moment you guess again, you're risking the entire accumulated amount on a 6-in-13 flip.

• Cash out → you receive bet × current multiplier, the bet resolves, done.

• Guess again → correct grows the multiplier; wrong loses everything.

There is no partial cash-out and no insurance. The tension is the product.

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Limits

Parameter	Value
Minimum bet	3 USD (configurable per game via core)
House edge	Configurable, 2%–5%
Per-guess multiplier factor	~1.9567× at 2% edge
Default multiplier cap	25× (~5 consecutive correct guesses)
Push	Drawing an 8 - multiplier unchanged, run continues
Cancellation	Admin/resolver only; refunds original stake, forfeits accumulated multiplier

Supported collaterals: USDC, WETH, $OVER. Free bets supported via the isFreeBet flag on placeBet.

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User guide

1. Open Hi-Lo

Select Hi-Lo from the casino lobby. Set your stake and collateral.

2. Make your first guess

Choose Above or Below. This places the bet and submits your first guess in a single transaction.

3. See the card

When the VRF callback arrives, the card is revealed. If you were right, your multiplier ticks up and it's your turn again. If wrong, the bet is over.

4. Press or cash out

Decide: guess again to push your multiplier higher, or hit Cash Out to bank bet × multiplier.

5. Resolution

Cashing out (or guessing wrong, or hitting the cap) resolves the bet. Your full run - every guess, every card, the multiplier after each step - is stored on-chain and shown in your history.

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Why this matters

The appeal of Hi-Lo is entirely psychological: the question of whether to press your luck one more time. That only works if you trust that the next card is genuinely random and not weighted against you precisely when your multiplier gets juicy.

On a centralized site, nothing stops the operator from nudging the draw against players sitting on a big multiplier - and you'd never know. On Overtime, each card comes from a fresh Chainlink VRF request that doesn't exist until you commit to the guess. The 6-in-13 odds are fixed by the rank of 8 splitting the deck, the multiplier factor is a published formula, and the whole run is reconstructable from the chain. The only thing deciding whether you win is the card. Which is the entire point.