Astro Boy - Omega Factor (c) 2003 Sega Enterprises, Limited.
GAME ID: AGB-BTAE-USA
The game went through massive changes when it was ported from Japan. The Japanese version only has Easy and Difficult difficulty settings. The International versions removed these in favor of Normal and Hard, with Normal as a re-balanced version of the original Difficult. The international versions also add a health meter for the bosses, language selection, a couple new enemies, adjusts some of the level layouts, and fixes some of the slowdown.