Unlock Hopper 7
Unlock Hopper 7 mode by clearing Killer 8 mode. Hopper 7 only plays through the
first stage.

Thick Blood & Serum
Thick blood is not carried over from stage to stage, but serum is. The blood
machine in each stage will cease to function if you revisit the stage, so learn
to collect as much thick blood as possible in a stage and break the machine
before moving on.

Unlock Killer 8
Clear the game and unlock Killer 8 mode, where the changes include:
Enemy critical spots are invisible
Enemy explosions do five times normal damage
Clue and map icons are hidden on the map menu