In Day 3 of my 10 Days of Blockchain series, I start wiring up the actual Rock, Paper, Scissors logic for a decentralized app using Reach (and deploying to Algorand). Before we even touch the “game,” I break it down into the components we need to represent in code: players (Alice and Bob), hands (rock/paper/scissors as 0/1/2), and outcomes (Bob wins/draw/Alice wins as 0/1/2). Then I define a shared participant interact interface called `Player` so the backend knows it can ask both participants for a move (`getHand`) and tell them the result (`seeOutcome`). On the frontend, I implement those behaviors: I set up arrays for hands and outcomes, build a reusable `Player` constructor, randomly pick a move using `Math.random()` + `Math.floor()`, and log what each player chose. On the backend in Reach, I show how decentralized “simultaneous reveal” isn’t really a thing, so we pick an order: Alice publishes first, then Bob publishes, and the consensus network computes the outcome using a clean modulo trick. Finally, I use `each` to send the outcome back to both frontends—because the whole point is that consensus guarantees everyone agrees on the result.