diff --git a/.github/.keep b/.github/.keep
new file mode 100644
index 0000000..e69de29
diff --git a/README.md b/README.md
index cab3c08..76507d5 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,4 @@
+[![Review Assignment Due Date](https://classroom.github.com/assets/deadline-readme-button-22041afd0340ce965d47ae6ef1cefeee28c7c493a6346c4f15d667ab976d596c.svg)](https://classroom.github.com/a/W3nV4mdD)
 # Banking management
 
 ## Overview
diff --git a/src/__tests__/real.test.ts b/src/__tests__/real.test.ts
index 443229c..c958918 100644
--- a/src/__tests__/real.test.ts
+++ b/src/__tests__/real.test.ts
@@ -1,16 +1,17 @@
-import { describe, beforeEach, it, expect } from 'vitest';
-import { TestFactory } from './helpers/TestFactory';
-import type { TestFixtures } from './helpers/TestFactory';
+import { describe, beforeEach, it, expect } from "vitest";
+import { TestFactory } from "./helpers/TestFactory";
+import type { TestFixtures } from "./helpers/TestFactory";
 
-describe('Bank Transfer Tests', () => {
+describe("Bank Transfer Tests", () => {
   let fixtures: TestFixtures;
 
   beforeEach(() => {
     fixtures = TestFactory.createFixtures();
   });
 
-  it('should allow transfer between accounts', () => {
-    const { bank, aliceUserId, bobUserId, aliceAccountId, bobAccountId } = fixtures;
+  it("should allow transfer between accounts", () => {
+    const { bank, aliceUserId, bobUserId, aliceAccountId, bobAccountId } =
+      fixtures;
 
     // Initial balances
     const aliceAccount = bank.getAccount(aliceAccountId);
@@ -26,19 +27,27 @@ describe('Bank Transfer Tests', () => {
     expect(bobAccount.getBalance()).toBe(800);
   });
 
-
-  it('should not allow transfer with insufficient funds', () => {
+  it("should not allow transfer with insufficient funds", () => {
     const { bank, aliceUserId, bobUserId } = fixtures;
 
     expect(() => {
       bank.send(aliceUserId, bobUserId, 2000);
-    }).toThrow('Insufficient funds');
+    }).toThrow("Insufficient funds");
   });
 
-  it('should allow transfer with negative balance', () => {
-    const { bank, bankAllowsNegative, aliceUserId, bobUserId, aliceAccountAllowsNegativeId, bobAccountId } = fixtures;
-
-    const aliceAccountAllowsNegative = bankAllowsNegative.getAccount(aliceAccountAllowsNegativeId);
+  it("should allow transfer with negative balance", () => {
+    const {
+      bank,
+      bankAllowsNegative,
+      aliceUserId,
+      bobUserId,
+      aliceAccountAllowsNegativeId,
+      bobAccountId,
+    } = fixtures;
+
+    const aliceAccountAllowsNegative = bankAllowsNegative.getAccount(
+      aliceAccountAllowsNegativeId
+    );
     const bobBankId = bank.getId();
     const bobAccount = bank.getAccount(bobAccountId);
 
diff --git a/src/__tests__/simple.test.ts b/src/__tests__/simple.test.ts
index 49bb5f6..2d9ad42 100644
--- a/src/__tests__/simple.test.ts
+++ b/src/__tests__/simple.test.ts
@@ -1,57 +1,59 @@
-import { describe, it, expect } from 'vitest';
-import User from '@/models/user';
-import Bank from '@/models/bank';
-import BankAccount from '@/models/bank-account';
-import TransactionService from '@/services/TransactionService';
-
-
-describe('Banks', () => {
-  it('has a bank class', () => {
+import { describe, it, expect } from "vitest";
+import User from "@/models/user";
+import Bank from "@/models/bank";
+import BankAccount from "@/models/bank-account";
+import TransactionService from "@/services/TransactionService";
+
+describe("Banks", () => {
+  it("has a bank class", () => {
     expect(Bank).toBeDefined();
   });
 
-  it('can create a bank', () => {
+  it("can create a bank", () => {
     const bank = Bank.create();
     expect(bank.getId()).toBeDefined();
   });
 
-  it('can create a bank account', () => {
+  it("can create a bank account", () => {
     const bank = Bank.create();
     const bankAccount = bank.createAccount(100);
     expect(bankAccount.getId()).toBeDefined();
   });
 });
 
-
-describe('Users', () => {
-  it('has a user class', () => {
+describe("Users", () => {
+  it("has a user class", () => {
     expect(User).toBeDefined();
   });
 
-  it('can create a user', () => {
-    const user = User.create('Firstname Lastname', []);
+  it("can create a user", () => {
+    const user = User.create("Firstname Lastname", []);
     expect(user).toBeDefined();
   });
 
-  it('can create a user with accounts', () => {
+  it("can create a user with accounts", () => {
     const bank = Bank.create();
     const bankAccount1Id = bank.createAccount(100).getId();
     const bankAccount2Id = bank.createAccount(200).getId();
     const bankAccount3Id = bank.createAccount(300).getId();
 
-    const user = User.create('Firstname Lastname', [bankAccount1Id, bankAccount2Id, bankAccount3Id]);
+    const user = User.create("Firstname Lastname", [
+      bankAccount1Id,
+      bankAccount2Id,
+      bankAccount3Id,
+    ]);
     expect(user).toBeDefined();
   });
 });
 
-describe('Accounts', () => {
-  it('has an account class', () => {
+describe("Accounts", () => {
+  it("has an account class", () => {
     expect(BankAccount).toBeDefined();
   });
 });
 
-describe('Transactions', () => {
-  it('has a transaction service', () => {
+describe("Transactions", () => {
+  it("has a transaction service", () => {
     expect(TransactionService).toBeDefined();
   });
 });
diff --git a/src/helpers/TestFactory.ts b/src/helpers/TestFactory.ts
new file mode 100644
index 0000000..b8cc876
--- /dev/null
+++ b/src/helpers/TestFactory.ts
@@ -0,0 +1,31 @@
+// ...existing imports...
+
+export class TestFactory {
+  static createFixtures(): TestFixtures {
+    GlobalRegistry.clear();
+
+    // Create users first
+    const aliceUser = User.create("Alice");
+    const bobUser = User.create("Bob");
+
+    // Create accounts and associate with users
+    const aliceAccount = bank.createAccount(1000, aliceUser.getId());
+    const bobAccount = bank.createAccount(500, bobUser.getId());
+    const aliceAccountAllowsNegative = bankAllowsNegative.createAccount(
+      200,
+      aliceUser.getId()
+    );
+
+    // ...rest of your code...
+
+    return {
+      bank,
+      bankAllowsNegative,
+      aliceUserId: aliceUser.getId(),
+      bobUserId: bobUser.getId(),
+      aliceAccountId: aliceAccount.getId(),
+      bobAccountId: bobAccount.getId(),
+      aliceAccountAllowsNegativeId: aliceAccountAllowsNegative.getId(),
+    };
+  }
+}
diff --git a/src/models/bank-account.ts b/src/models/bank-account.ts
new file mode 100644
index 0000000..f193021
--- /dev/null
+++ b/src/models/bank-account.ts
@@ -0,0 +1,51 @@
+import { BankAccountId } from "@/types/Common";
+
+export default class BankAccount {
+  private id: BankAccountId;
+  private balance: number;
+  private isNegativeAllowed: boolean;
+
+  constructor(initialBalance: number, isNegativeAllowed: boolean = false) {
+    this.id = this.generateId();
+    this.balance = initialBalance;
+    this.isNegativeAllowed = isNegativeAllowed;
+  }
+
+  private generateId(): BankAccountId {
+    return `account_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;
+  }
+
+  getId(): BankAccountId {
+    return this.id;
+  }
+
+  getBalance(): number {
+    return this.balance;
+  }
+
+  deposit(amount: number): void {
+    if (amount <= 0) {
+      throw new Error("Deposit amount must be positive");
+    }
+    this.balance += amount;
+  }
+
+  withdraw(amount: number): void {
+    if (amount <= 0) {
+      throw new Error("Withdrawal amount must be positive");
+    }
+
+    if (!this.isNegativeAllowed && this.balance < amount) {
+      throw new Error("Insufficient funds");
+    }
+
+    this.balance -= amount;
+  }
+
+  setBalance(balance: number): void {
+    if (!this.isNegativeAllowed && balance < 0) {
+      throw new Error("Negative balance not allowed");
+    }
+    this.balance = balance;
+  }
+}
diff --git a/src/models/bank.ts b/src/models/bank.ts
new file mode 100644
index 0000000..3e79c04
--- /dev/null
+++ b/src/models/bank.ts
@@ -0,0 +1,104 @@
+import { BankAccountId, UserId } from "@/types/Common";
+import BankAccount from "./bank-account";
+import GlobalRegistry from "@/services/GlobalRegistry";
+
+interface BankOptions {
+  isNegativeAllowed?: boolean;
+}
+
+export default class Bank {
+  private id: string;
+  private accounts: Map<BankAccountId, BankAccount>;
+  private isNegativeAllowed: boolean;
+
+  constructor(options: BankOptions = {}) {
+    this.id = this.generateId();
+    this.accounts = new Map();
+    this.isNegativeAllowed = options.isNegativeAllowed || false;
+    GlobalRegistry.registerBank(this);
+  }
+
+  private generateId(): string {
+    return `bank_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;
+  }
+
+  static create(options?: BankOptions): Bank {
+    return new Bank(options);
+  }
+
+  getId(): string {
+    return this.id;
+  }
+
+  createAccount(initialBalance: number): BankAccount {
+    const account = new BankAccount(initialBalance, this.isNegativeAllowed);
+    this.accounts.set(account.getId(), account);
+    return account;
+  }
+
+  getAccount(accountId: BankAccountId): BankAccount {
+    const account = this.accounts.get(accountId);
+    if (!account) {
+      throw new Error(`Account ${accountId} not found`);
+    }
+    return account;
+  }
+
+  hasAccount(accountId: BankAccountId): boolean {
+    return this.accounts.has(accountId);
+  }
+
+  send(
+    fromUserId: UserId,
+    toUserId: UserId,
+    amount: number,
+    toBankId?: string
+  ): void {
+    const fromUser = GlobalRegistry.getUser(fromUserId);
+    const toUser = GlobalRegistry.getUser(toUserId);
+
+    if (!fromUser || !toUser) {
+      throw new Error("User not found");
+    }
+
+    const fromAccountIds = fromUser.getAccountIds();
+    const toAccountIds = toUser.getAccountIds();
+
+    if (fromAccountIds.length === 0 || toAccountIds.length === 0) {
+      throw new Error("User has no accounts");
+    }
+
+    // Find accounts that belong to this bank
+    const fromAccountId = fromAccountIds.find((id) => this.hasAccount(id));
+    const toAccountId = toAccountIds.find((id) => this.hasAccount(id));
+
+    if (!fromAccountId) {
+      throw new Error("Sender has no account in this bank");
+    }
+
+    const fromAccount = this.getAccount(fromAccountId);
+
+    // Determine target bank and account
+    let toBank: Bank;
+    let toAccount: BankAccount;
+
+    if (toBankId && toBankId !== this.id) {
+      toBank = GlobalRegistry.getBank(toBankId);
+      const targetAccountId = toAccountIds.find((id) => toBank.hasAccount(id));
+      if (!targetAccountId) {
+        throw new Error("Recipient has no account in target bank");
+      }
+      toAccount = toBank.getAccount(targetAccountId);
+    } else {
+      if (!toAccountId) {
+        throw new Error("Recipient has no account in this bank");
+      }
+      toBank = this;
+      toAccount = this.getAccount(toAccountId);
+    }
+
+    // Perform the transfer
+    fromAccount.withdraw(amount);
+    toAccount.deposit(amount);
+  }
+}
diff --git a/src/models/index.ts b/src/models/index.ts
new file mode 100644
index 0000000..4b1c76f
--- /dev/null
+++ b/src/models/index.ts
@@ -0,0 +1,3 @@
+export { default as User } from "./user";
+export { default as Bank } from "./bank";
+export { default as BankAccount } from "./bank-account";
diff --git a/src/models/user.ts b/src/models/user.ts
new file mode 100644
index 0000000..46394e1
--- /dev/null
+++ b/src/models/user.ts
@@ -0,0 +1,45 @@
+import { UserId, BankAccountId } from "@/types/Common";
+import GlobalRegistry from "@/services/GlobalRegistry";
+
+export default class User {
+  private id: UserId;
+  private name: string;
+  private accountIds: BankAccountId[];
+
+  constructor(name: string, accountIds: BankAccountId[]) {
+    this.id = this.generateId();
+    this.name = name;
+    this.accountIds = accountIds;
+    GlobalRegistry.registerUser(this);
+  }
+
+  private generateId(): UserId {
+    return `user_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;
+  }
+
+  static create(name: string, accountIds: BankAccountId[]): User {
+    return new User(name, accountIds);
+  }
+
+  getId(): UserId {
+    return this.id;
+  }
+
+  getName(): string {
+    return this.name;
+  }
+
+  getAccountIds(): BankAccountId[] {
+    return [...this.accountIds];
+  }
+
+  addAccount(accountId: BankAccountId): void {
+    if (!this.accountIds.includes(accountId)) {
+      this.accountIds.push(accountId);
+    }
+  }
+
+  removeAccount(accountId: BankAccountId): void {
+    this.accountIds = this.accountIds.filter((id) => id !== accountId);
+  }
+}
diff --git a/src/services/GlobalRegistry.ts b/src/services/GlobalRegistry.ts
new file mode 100644
index 0000000..ec4c6ec
--- /dev/null
+++ b/src/services/GlobalRegistry.ts
@@ -0,0 +1,33 @@
+import { UserId } from "@/types/Common";
+import User from "@/models/user";
+import Bank from "@/models/bank";
+
+export default class GlobalRegistry {
+  private static users: Map<UserId, User> = new Map();
+  private static banks: Map<string, Bank> = new Map();
+
+  static registerUser(user: User): void {
+    this.users.set(user.getId(), user);
+  }
+
+  static registerBank(bank: Bank): void {
+    this.banks.set(bank.getId(), bank);
+  }
+
+  static getUser(userId: UserId): User | undefined {
+    return this.users.get(userId);
+  }
+
+  static getBank(bankId: string): Bank {
+    const bank = this.banks.get(bankId);
+    if (!bank) {
+      throw new Error(`Bank ${bankId} not found`);
+    }
+    return bank;
+  }
+
+  static clear(): void {
+    this.users.clear();
+    this.banks.clear();
+  }
+}
diff --git a/src/services/TransactionService.ts b/src/services/TransactionService.ts
new file mode 100644
index 0000000..a433f2e
--- /dev/null
+++ b/src/services/TransactionService.ts
@@ -0,0 +1,34 @@
+import { UserId } from "@/types/Common";
+import GlobalRegistry from "./GlobalRegistry";
+import Bank from "@/models/bank";
+
+export default class TransactionService {
+  static transfer(
+    fromUserId: UserId,
+    toUserId: UserId,
+    amount: number,
+    bankId?: string
+  ): void {
+    const fromUser = GlobalRegistry.getUser(fromUserId);
+    const toUser = GlobalRegistry.getUser(toUserId);
+
+    if (!fromUser || !toUser) {
+      throw new Error("User not found");
+    }
+
+    // For now, we'll use the first bank in the registry
+    // In a real implementation, you'd want to specify which bank to use
+    const bank = bankId ? GlobalRegistry.getBank(bankId) : null;
+    if (!bank) {
+      throw new Error("No banks available");
+    }
+
+    bank.send(fromUserId, toUserId, amount);
+  }
+
+  static getTransactionHistory(userId: UserId): any[] {
+    // This would return transaction history for a user
+    // For now, return empty array
+    return [];
+  }
+}
diff --git a/src/types/common.ts b/src/types/common.ts
new file mode 100644
index 0000000..bea7b44
--- /dev/null
+++ b/src/types/common.ts
@@ -0,0 +1,2 @@
+export type BankAccountId = string;
+export type UserId = string;