Moved the game engine into its own unit and then made a failing test for it.

game_engine.cpp

@@ -0,0 +1,39 @@
+#include <map>
+#include <string>
+#include <fmt/core.h>
+#include <fmt/color.h>
+#include "game_engine.hpp"
+
+using namespace fmt;
+using namespace std;
+
+const auto ERROR = fmt::emphasis::bold | fg(fmt::color::red);
+
+GameEngine::GameEngine(int hp) : hit_points(hp) {};
+
+int GameEngine::determine_damage(string &type) {
+  try {
+    return damage_types.at(type);
+  } catch(std::out_of_range &err) {
+    print(ERROR, "BAD DAMAGE TYPE {}\n", type);
+    return 1000;
+  }
+}
+
+bool GameEngine::hit(string &type) {
+  int damage = determine_damage(type);
+  hit_points -= damage;
+
+  if(is_dead()) {
+    print(ERROR, "YOU DIED!\n");
+  } else {
+    println("DAMAGE {}, HP: {}", damage, hit_points);
+  }
+
+  // super dumb but I'll clean it up later
+  return is_dead();
+}
+
+bool GameEngine::is_dead() {
+  return hit_points <= 0;
+}