Add Simple Math Level

contracts/src/levels/index.js

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+import SimpleMath from './SimpleMath';
+
+export const levels = [
+  ...previousLevels,
+  {
+    name: "Simple Math",
+    contract: SimpleMath,
+    description: "Overflow the multiplication to solve the contract!"
+  }
+];

contracts/test/levels/SimpleMath.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+contract SimpleMath {
+    uint8 public result;
+
+    function multiply(uint8 a, uint8 b) public {
+        result = a * b; // players will try to overflow
+    }
+
+    function isSolved() public view returns (bool) {
+        return result < 255; // simple check for overflow
+    }
+}

contracts/test/levels/SimpleMath.test.js

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+const { expect } = require("chai");
+
+describe("SimpleMath Level", function () {
+  let contract;
+
+  beforeEach(async function () {
+    const SimpleMath = await ethers.getContractFactory("SimpleMath");
+    contract = await SimpleMath.deploy();
+    await contract.deployed();
+  });
+
+  it("should overflow the result", async function () {
+    await contract.multiply(20, 13); // 20*13 = 260 > uint8 max 255
+    const result = await contract.result();
+    expect(result).to.be.lt(260); // overflow happened
+  });
+});