bring server files into project.

src/lib/server/Game.ts

@@ -0,0 +1,25 @@
+import type { Id } from "./Id";
+import type { GameData } from "../GameData";
+import type { State } from "../State";
+
+export class Game implements GameData {
+	players: Id[];
+	isStarted: boolean;
+	state: State;
+
+	constructor() {
+		this.players = [];
+		this.isStarted = false;
+		this.state = {};
+	}
+
+	addPlayer(id: Id) {
+		this.players.push(id);
+	}
+
+	start() {
+		if (this.isStarted) throw new Error("game is already started");
+
+		this.isStarted = true;
+	}
+}