feat: implement game GCD

Makefile

@@ -20,4 +20,7 @@ brain-even:
 	./bin/brain-even
 
 brain-calc:
-	./bin/brain-calc
+	./bin/brain-calc
+
+brain-gcd:
+	./bin/brain-gcd

bin/brain-gcd

@@ -0,0 +1,9 @@
+#!/usr/bin/env php
+<?php
+
+use function BrainGames\Engine\runBrainGame;
+
+require_once __DIR__ . '/../src/bootstrap.php';
+
+$module = 'GcdGame';
+runBrainGame($module);

composer.json

@@ -20,7 +20,8 @@
     }
   ],
   "require": {
-    "wp-cli/php-cli-tools": "^0.11.19"
+    "wp-cli/php-cli-tools": "^0.11.19",
+    "ext-gmp": "*"
   },
   "bin": [
     "bin/brain-games",

src/Games/GcdGame.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace BrainGames\Games\EvenGame;
+
+use Exception;
+
+use const BrainGames\Utils\ModuleUtils\HANDLER_QUESTION;
+use const BrainGames\Utils\ModuleUtils\LOCATION_HANDLERS;
+use const BrainGames\Utils\ModuleUtils\LOCATION_SETTINGS;
+use const BrainGames\Utils\ModuleUtils\SETTING_RULES;
+
+return function ($module) {
+    $module[LOCATION_SETTINGS][SETTING_RULES] = 'Find the greatest common divisor of given numbers.';
+
+    $module[LOCATION_HANDLERS][HANDLER_QUESTION] = fn() => questionHandler();
+
+    return $module;
+};
+
+/**
+ * Returns a question and its expected answer.
+ *
+ * - 0: The question (string)
+ * - 1: The expected answer (string)
+ *
+ * @return array{
+ *     0: string,
+ *     1: string
+ * }
+ * @throws Exception
+ */
+function questionHandler(): array
+{
+    $firstNum = random_int(1, 100);
+    $secondNum = random_int(1, 100);
+
+    $expectedAnswer = gmp_gcd($firstNum, $firstNum);
+    $question = "$firstNum $secondNum";
+    return [$question, $expectedAnswer];
+}