message: Use string constants instead of hard-coding
diff: @@ -65,10 +65,10 @@ void DifficultySelect::init()
  default: rdbBeginner.checked(true); break;
  }
  - rdbBeginner.text("Beginner");
  - rdbEasy.text("Easy");
  - rdbMedium.text("Medium");
  - rdbHard.text("Hard");
  + rdbBeginner.text(constants::DIFFICULTY_BEGINNER);
  + rdbEasy.text(constants::DIFFICULTY_EASY);
  + rdbMedium.text(constants::DIFFICULTY_MEDIUM);
  + rdbHard.text(constants::DIFFICULTY_HARD);
  float longest_width = 0.0f;
  if (longest_width < rdbBeginner.width())
  