Coroutines are mostly working but they're kind of junk anyway. Feel free to tinker with this if you like.

game_engine.cpp

@@ -19,7 +19,7 @@ int GameEngine::determine_damage(string &type) {
     return damage_types.at(type);
   } catch(std::out_of_range &err) {
     print(ERROR, "BAD DAMAGE TYPE {}\n", type);
-    return 1000;
+    return 0;
   }
 }