The hit video game World of Warcraft (WoW) is going back to basics with the launch of WoW Classic this evening.
First released in 2004, the online multi-player game has evolved and changed dramatically over the years.
Many players had asked developer Blizzard Entertainment to revive the original version of the game, known as "classic" or "vanilla" WoW.
While not identical to the original, WoW Classic will replicate a majority of the features from the first game.
World of Warcraft is a fantasy game in which players roam the virtual world, fighting monsters and completing quests.
Blizzard said some players who had been given early access to the classic version - which is released at 23:00 BST on Monday - mistakenly thought some of the original features were errors.
The company has compiled a list of common complaints that are "not bugs" on its message board.
What set WoW apart?
"WoW's launch was a significant moment," says Piers Harding-Rolls, from the IHS Markit consultancy. "It had a broad impact on the gaming sector as a whole and especially the online gaming scene.
"The appeal and accessibility of the game meant it soon grew to millions of users in the West and broadened the audience for this type of game significantly.
"It was so popular in the US that Blizzard - then part of Vivendi - ran ads on TV with celebrity endorsements. This was pretty much unheard of back in 2004."
Oli Walsh, editor of video-game website Eurogamer, said: "The quality of the execution set it apart, along with Blizzard's ability to make this previously rather intimidating style of game approachable to a broad audience.
"It was, and remains, so well done that nothing has really supplanted it in 15 years - although many tried. Arguably, it was the first truly mass-market online game."
Why do some fans want Classic?
Luciano Frias-Andrade, who has played WoW since it was released in the UK in 2005, said the game had evolved considerably.
"Back then it was a very different world, with no short cuts. I remember spending a day 'walking' by foot from the human capital to the elven home town, just to be the first human there," he told the BBC. "When I arrived, it caused a sensation. Everyone said: 'A human, here? How?'"
He fondly remembers a bug that affected gameplay back in 2005, now known as the corrupted blood incident.
"One of the high-level bosses had a spell that damaged high-level players. Problem was, it was infectious and the programmers didn't count on players warping back home.
"The capital cities were littered with dead players and skeletons, because it instantly killed low-level players. They would respawn and instantly die again. It was like a real virus until the developers fixed it."
He told the BBC he was not sure whether he would commit to playing Classic long term.
"I'll give Classic a go, but honestly, it took for ever to do anything. I'm not sure if I'd have the time.
Another long-term fan, Valen Kross, agreed.
"When WoW started it was a great game for its time. But it was a massive time sink - much more than it is now. I just don't want to put in all that time," he said.
"The main reason why I play WoW is the rich lore of of the world. Story is the most important thing to me, so playing the vanilla game is essentially a time bubble, in which the story can't go anywhere."
But Aaron McConnell, who plays as Typhane in the Maelstrom realm, is more excited.
"It's an entirely different game right now, compared to when it first launched," he said.
"The scale of things added over the years is too much to put into words. Classic is worth its own game outright. I'm definitely going to play it. It's a huge change of pace."
Will Classic endure?
At its peak, World of Warcraft had about 12 million active players, though numbers have since declined.
However, Blizzard expects so much interest in WoW Classic that players will have to queue to enter certain realms.
One of the game's producers has encouraged fans to reserve their player name ahead of the launch.
"The release of WoW Classic will be a nostalgia trip for gamers who left WoW many years ago - and a fresh experience for gamers that played the game later in its lifecycle," said Mr Harding-Rolls.
"Inevitably there will be some aspects of WoW Classic that might feel of its time, but it has also been updated with better graphics and other features to make the transition easier for gamers in 2019."
Another online title - Runescape - did something similar.
Mr Walsh suggested that many gamers may not take long to tire of the latest revival.
"I think a lot of people will enjoy reliving memories in it for a month or two, but after a while they'll move on and only that hardcore will remain," he said.
"For Blizzard, it's more of a vehicle to keep WoW fresh and get lapsed players excited about it.
"It's significant in another sense, though - this is [one of the few times] anyone has officially recreated an old version of an evolving online game, and as such, it's a fascinating experiment."