The final upgrade to the two single-player games was made available on February 18, 2005.
By contrast, many single-player games are built around a compelling story.
"But I end up feeling in a single-player game that there's no one to share your accomplishments with."
You mean there are still a lot of people who like single-player games?
The single-player game was considered too easy and too short.
You can finish the single-player game in about 20 minutes.
That said, it's primarily a single-player game, and those issues doesn't really affect the experience much for me.
In the single-player game, a form of gravity is the opposition.
From the beginning of the single-player game, all players' characters begin at the base level.
In a single-player game, there is a story mode feature.