Designed for European markets. While the Xbox 360 largely mitigated the "PAL slowdown" seen in earlier generations (like the SNES or N64) by supporting 60Hz modes, the PAL retail discs remain region-locked to European consoles.
The standard version for American and Canadian consoles. It runs at the native 60Hz signal standard.
A standard ISO for Perfect Dark Zero is roughly 6GB to 7GB, fitting on a standard DVD-DL (Dual Layer) disc. Why It Matters Today
At launch, it supported up to 32 players online, a massive feat for consoles at the time.
It opted for a high-contrast, "plastic" aesthetic that showcased the Xbox 360's new shader capabilities and lighting effects.