The 2000s in video gaming was a decade that was primarily dominated by Sony, Nintendo, the newcomer Microsoft, and their respective systems. Sega, being Nintendo's main rival in the 1980s and 1990s, left the console market in 2002 in favor of returning to the third party company they once were. Overall the decade saw the last of the low resolution three-dimensional polygons of the 1990s with the emergence of High Definition games, and often focused on developing immersive and interactive environments, implementing realistic physics, and improving artificial intelligence.