Though the majority of the game is unchanged, all health kits are redrawn to display a red and white pill instead of the medical red cross from the original. This is likely due to ongoing trademark disputes with the American Red Cross over use and licensing of the "red cross" symbol.
The names of several achievements ("Rip and Tear", "The Great Communicator", "A Man and a Half", "You Have Huge Guts", "An Important Looking Door", "A Really Big Gun", "Superior Firepower") are quotes from the infamously silly Doom comic
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