Successful completion of the objectives over all missions in all difficulties above 'Easy' results in the awarding of Silver Weapons (infinite bullets) and unlocking the M16-A2 (40mm underslung grenade launcher attachment) as the starting default weapon with infinite 40mm grenades. When unlocked, these features are permanent and cannot be removed without starting a fresh storyline. Development Criterion intended to "do for shooting what Burnout did for racing - tear it apart", with dual emphasis on destructible environments and the handling and behavior of real-world firearms. Bullets that hit buildings, terrain and objects leave visible damage; moreover, the guns are rendered with great detail and accuracy, though some weapons' features are stylized or exaggerated. The emphasis on the appearance, function, and sounds of the weapons led the developer to label the game as "Gun-Porn". Another notable and original feature is the use of real-time blur while reloading, giving a depth of field and more perspective to the game. Similarly, when the player drops below two bars of health, the screen turns black and white, the sound of the character's heartbeat become the dominant noise and the game goes into slow motion, and the large and small motors in the control pads match the sound of systolic and diastolic part of the heartbeat. The game was not developed with an overarching plot structure in mind and this was implemented as something of an afterthought towards the end of development. The initial idea for relating the plot in-game came from Black's director, Alex Ward, who wanted to have a radio-play-style voiceover spoken over a 'black' screen. Sound Emphasizing the game's action film heritage, sound effects for the weapons in the game were based on various sounds from films. For example, Bruce Willis' Heckler & Koch MP5 in Die Hard, Jack Bauer's pistol in 24, and Arnold Schwarzenegger's Uzi in True Lies. Realizing in the chaos of a heavy gun battle the heavy mix of sound and music would produce a cacophony of noise, the sound designers developed the "choir of guns" concept. Whereas, traditionally in a shooter game, each weapon model would be assigned a different sound, Black assigns each enemy their own "voice", similar to the way in which each member of a choir would have their own distinct voice. For example, there are three enemies firing, one would be assigned a low voice, another a medium voice, and the third a