As the original Baldur's Gate games leak for Game Pass again, fans reminisce over the bizarre D&D systems that drove BioWare's CRPGs

gamesradar.com:

The original Baldur's Gate games appear to have leaked for Xbox Game Pass, causing players to reminisce about the bizarre rulesets of the D&D editions they were based on.

As noted by TrueAchievements, earlier this week Game Pass subscribers received a push notification from the subscription service's app, suggesting that Baldur's Gate 1 and Baldur's Gate 2 were available on the service. That's not currently the case, as clicking the notification simply takes you to the games' store page, but it's also not the first time this has happened - a similar notification was pushed in August. Once might have been a mistake, but twice seems like an unlikely coincidence, implying that the classic CRPGs are on their way to Game Pass at some point in the future.

Unfortunately, while Baldur's Gate 1 and 2 are classics for a reason, they're not always the most accessible games. Baldur's Gate 3 is built on the Fifth Edition (5e) of Dungeons & Dragons, a system that might seem complicated from the outside, but is one of the more accessible versions of the TTRPG. 

By contrast, the first two games in the series are based on Advanced Dungeons & Dragons' Second Edition, which feature the infamous THAC0 system. THAC0 - as explained by shellshocked Baldur's Gate fans over on Reddit- stands for 'To Hit Armor Class 0', and is a version of the hit chance and AC system that's present in current forms of D&D that flips what you might expect from 5e on its head. In the modern game, the higher your Armor Class (AC), the better defended you are, and the less likely your enemies' attacks are to hit. THAC0 inverted that idea, meaning that a lower AC was actually better.

Realistically, that means that THAC0 isn't actually that complicated - it's a plus