class Save{
  //These can be static or non-static
  AchievementData achievements;
  PlayerData player;
}

class AchievementData{
  bool killedSomething;
  int milesWalked;
}

class PlayerData{
  InventoryData inventory;
  int health;
}

class InventoryData{
  List<ItemData> items;
}

class ItemData{
  int id;
}