1.2.1 small changes

added screen shake, particle explosion and sound effect to big Gift Boxes
added screen shake to player death
changed flat enemy defense from -10/+10 to -30/+30 and added it for bosses and elites
- outside of Horde Mode, the negative modifiers are currently hidden and happen when specific conditions are met or triggered in the main levels
- the positive modifiers can be triggered by defeating Gift Boxes after the letter for Bella's unlock condition is acquired
peaking pig's bacon bullets now properly despawn after a while