标签：#anchor

A full-stack, peer-to-peer coinflip betting game on Solana A full-stack, peer-to-peer coinflip betting game on Solana. Players connect a wallet, create or join on-chain game rooms, and compete head-to-head for 2× the stake. The UI updates in real time over WebSockets, outcomes are resolved on-chain with Orao VRF, and the backend tracks rooms, chat, and match history in MongoDB. I open-sourced coinflip-casino for developers in Solana / Anchor smart contract development . This post walks through what it does, how the pieces fit together, and how to run it locally. Live demo / site: https://www.flip.is/ Why I built this Learn full-stack Web3 game architecture (wallet + program + backend + UI) Study provably fair randomness with on-chain VRF integration Fork and customize a peer-to-peer on-chain betting room model Most tutorials stop at a smart contract or a UI mockup. I wanted a complete vertical slice — wallet flow, on-chain logic, backend state, and a responsive frontend — so you can study or fork a production-shaped codebase. What it does Create a room — Pick Head or Tail, set bet amount, choose SOL or SPL token. Join a room — Browse open games in the live lobby and match against another player. PvP coinflip — When two players are in the same room, the backend triggers on-chain resolution. 2× payout — The winner receives double the bet (fees apply on-chain). Room expiration — Open rooms older than 5 minutes with no opponent are expired and refunded automatically. Portfolio stats — Win count and total games per wallet. Wallet connect — players sign in with a Solana wallet Peer-to-peer rooms — create or join head-to-head matches Architecture at a glance Wallet layer — users connect a Web3 wallet to sign transactions On-chain program — Anchor/Rust logic for escrow, rooms, and settlement Randomness — verifiable flip outcomes via Orao VRF on Solana Real-time layer — WebSocket events push room and flip state to the UI Persistence — MongoDB stores rooms, chat, and historic

I spent a week building a counter program in Anchor — the Rust framework for writing Solana programs. By the end I had two instructions, one authorization constraint, and a test suite I could actually trust. Here is what I built, how I tested it, and the moment I proved the tests were real. Start Here: The Accounts Struct If you come from Web2, this is the part that looks the strangest: #[derive(Accounts)] pub struct Initialize { #[account( init, payer = authority, space = 8 + Counter::INIT_SPACE, )] pub counter : Account , #[account(mut)] pub authority : Signer , pub system_program : Program , } In a Web2 backend, your handler receives a request object and talks to a database. On Solana, there is no database; there are accounts. Every account your instruction needs to read or write must be declared upfront, before the handler runs. Anchor validates them before your code ever executes. Here is what each field does: counter — the account being created. The init constraint tells Anchor to make a CPI to the System Program, allocate 8 + Counter::INIT_SPACE bytes, and fund it from authority . The 8 is for the discriminator Anchor stamps on every account so the program can later verify "this is mine." authority — the wallet signing and paying for the transaction. mut because its SOL balance is decreasing to fund the new account. system_program — required any time you create accounts. Anchor checks that the address matches the real System Program. The accounts struct is the schema. The handler is the logic. The Handlers pub fn initialize ( ctx : Context ) -> Result { let counter = & mut ctx .accounts.counter ; counter .authority = ctx .accounts.authority .key (); counter .count = 0 ; Ok (()) } ctx.accounts gives you typed access to every account declared in the struct. The handler is short because Anchor already did the hard work: allocating the account, checking the signer, paying the rent. Your code just sets the initial values. pub fn increment ( ctx : Context ) -> Resu

Despite the countless number of online resources, it’s easy to get confused when trying to center an element. There are documented solutions, but do you really understand why the code you picked works? Let's look at the current state of centering options today in 2026. The State of CSS Centering in 2026 originally handwritten and published with love on CSS-Tricks . You should really get the newsletter as well.