With the original bosses all bad - they usually look like enlarged copies of ordinary enemies. Just kill them have much longer.
In the subconscious of some of the objects change their shape. For example, the boiler turns into a skull.
You've probably heard about the syndrome of Russian shooter. With very few exceptions, domestic developers have stubbornly refused to receive quality games in this genre. Strategies are able to do, quests, too. Even RPG, simulations and action go, but the trouble with FPS. And, apparently, this rule applies to the whole of Eastern Europe.