Add new gcd game

Author: thedoorbell

bin/brain-gcd.js

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+#!/usr/bin/env node
+
+import run from '../src/games/gcd.js';
+
+run();

src/games/gcd.js

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+import playGame from '../index.js';
+
+const rules = 'Find the greatest common divisor of given numbers.';
+
+const findGcd = () => {
+  const firstNum = Math.floor(Math.random() * 150) + 1;
+  const secondNum = Math.floor(Math.random() * 50) + 1;
+  const minNum = Math.min(firstNum, secondNum);
+  const question = `${firstNum} ${secondNum}`;
+  let correctAnswer = 1;
+
+  for (let i = 2; i <= minNum; i += 1) {
+    if (firstNum % i === 0 && secondNum % i === 0) {
+      correctAnswer = i;
+    }
+  }
+
+  return [question, String(correctAnswer)];
+};
+
+export default () => playGame(rules, findGcd);