The year is 2005. Polyphony Digital is coming off Gran Turismo 4, one of the greatest racing games ever made. All it really needs to do is focus its efforts on making Gran Turismo 5 as good as it can be, taking advantage of the capabilities of the much-hyped PlayStation 3, which has still yet to come out. Unfortunately, Polyphony and its chief Kazunori Yamauchi were determined to do literally anything but that in 2005, leading to the confusing announcement and prompt cancellation of Gran Turismo HD — a product that, almost 20 years on, I’m still not entirely sure I understand. GTHD was really two games, and here’s how IGN explained them at the time:
In GTHD Premium, players get to sample a portion of Gran Turismo 5, with two brand new courses and 30 cars that fully make use of the PS3's capabilities. This mode will offer arcade-style races, but it continues the spirit of the series by serving as a “pure driving simulator.” Premium mode will not have any elements of the Series Gran Turismo mode, where you earn new cars and courses by clearing events. All cars and courses will be available from the start. [...]
The second mode of play is GTHD Classic, an online racing mode that’s based off both the Gran Turismo HD demo from E3 and the PlayStation 2 beta test that Polyphony conducted a few months back in Japan. [...] In Classic mode, players begin with no cars or courses. New rides and tracks are added via downloads with over 750 cars and 50 courses to choose from. SCE will charge for the downloadable extras, and while pricing hasn’t been finalized, we expect each car to cost between 50 and 100 yen (50 cents to 1 dollar) each. Polyphony plans on adding more cars and courses on a weekly or monthly basis, with some cars available in limited quantities.
So, to sum up, GTHD “Premium” was more or less the free demo released as Gran Turismo HD Concept in 2006. Except not really, because Concept only had one track and far fewer than 30 cars. Also, GTHD “Classic” — seemingly a cut-down version of Gran Turismo 4 Online Test Version with no conventional single-player campaign, loads of microtransactions, more competitors in races and even a few bikes from Tourist Trophy — simply never came out. Both were scrapped in favor of Gran Turismo 5 Prologue, which finally launched with online play globally in 2008.