Gacha Starter

Two working demos of the Collector Crypt gacha API in one app:

Route	Chain	Pay with
/	Solana	SPL USDC — the server builds the transaction, you sign it
/evm	EVM (multichain)	An ERC-20 lane — you call pay() yourself

Both are thin clients. Every route under app/api/ is a small forwarder that attaches your x-api-key; the roll, the VRF, the inventory and the payouts all live in the gacha API.

Getting Started

1. Go to Privy and get an app id + client id.
2. Get an API key from Collector Crypt on Discord. One key covers both demos — the API validates x-api-key the same way on /api/evm/* as on the Solana routes, so EVM mode needs no new secret.
3. Copy .env.example to .env and fill it in.
4. Deploy to Vercel.

Test funds

Solana (/) — dev USDC from https://spl-token-faucet.com/?token-name=USDC-Dev, mint Gh9ZwEmdLJ8DscKNTkTqPbNwLNNBjuSzaG9Vp2KGtKJr.

EVM (/evm) — you need two things:

• Native ETH for gas. The machine sponsors the gas for the card mint only; your approve, pay and sellBack are ordinary transactions you pay for. Base Sepolia: https://www.alchemy.com/faucets/base-sepolia.
• The payment token. On a testnet tUSDC lane the page shows a Mint 100 tUSDC button — that token's mint() is permissionless, so you can top yourself up. Real Base Sepolia USDC is scarce and cannot be minted; prefer the tUSDC lane.

Solana vs EVM: what changes

	Solana	EVM
Payment	server-built transaction you sign	you call pay(token, amount, memo) yourself
Prize	NFT transferred to you	ERC-721 minted to you
Buyback	server-built transaction	server-signed quote, you call sellBack
Refunds	supported	none — payments are final
Networks	one	several — carry chainId everywhere
rarity	"Epic"	"epic" — read rarity_label for the shared form
Values	base units	whole USD (insured_value, buyback_amount)
points	earned per pack	always 0

Full contract: https://docs.collectorcrypt.com/gacha/evm-api

Things this demo does on purpose

• sellBack is sent with the quote's suggestedGasLimit, never a bare estimate. The call pulls the NFT, pays you and burns the card in one transaction, and EIP-150 forwards only 63/64 of the remaining gas to that final burn — a tight estimate starves it and the whole atomic sell unwinds. Measured over a 500-pack run that hit about 15% of sales. Over-asking is free; unused gas is refunded.
• Amounts are never recomputed from a human number. amount and refundAmountBase come back in base units and are passed through verbatim. Decimals are per lane and are not always 6.
• chainId travels with every token id. The gateway, vault and card sit at the same address on nearly every chain, so token 2615 on Base and on Robinhood are different cards.
• The memo is persisted before any money moves, and the pay transaction hash the instant it exists — before its receipt is awaited. Payments are final, so a closed tab must not be able to strand one. /evm shows an "Unfinished packs" banner that completes them; opening is idempotent.
• Your cards are read from the card contract, not from an NFT API. CollectorCrypt is ERC721Enumerable, so balanceOf + tokenOfOwnerByIndex over multicall3 is the authoritative list: no API key, nothing to index, no lag behind the mint, and it works on Robinhood Chain, which the hosted NFT APIs do not cover. localStorage is kept only for the memo and the resume banner.
• "In the machine" and "Your cards" are two different questions, from two different APIs. /api/getNfts returns the machine's POOL — its handler reads code, rarity, page and limit and ignores an owner param, so it can never answer what a wallet holds. The wallet grid comes from the Collector Crypt cards API on Solana, and straight off the card contract on EVM.
• Balances are read client-side. On EVM a balance needs no backend, unlike the Solana /api/getUsdcBalance route which exists because the RPC lives server-side.
• The chain and lane picker is driven by GET /api/evm/chains at runtime. Nothing is hardcoded — paused, not-ready and unknown chains are greyed out with the reason.

showWalletUIs: false in app/providers.tsx keeps the demo fast by signing without a confirmation step. A real product should set it to true so people see what they are paying.

Documentation

• Solana API: https://docs.collectorcrypt.com/gacha/api
• EVM API: https://docs.collectorcrypt.com/gacha/evm-api
• Provable fairness: https://docs.collectorcrypt.com/gacha/vrf