Blizzard has completely rebooted its StarCraft 2 mod Blizzard DOTA.

The version of the game shown at BlizzCon last year has been "flattened", senior game designer Jonny Ebbert told Eurogamer.

Blizzard DOTA is one of four internally-developed mods for StarCraft II, and intended for release on or near the launch of StarCraft 2 expansion Heart of the Swarm.

It's a variation on the ever-popular Defense of the Ancients, which began life as a Warcraft III mod.

Fans had hoped it would launch this year, but it now looks a dead cert for 2012.

"Getting it right and just meeting the Blizzard quality bar, and questioning a lot of the assumptions behind the genre, which is what we do at Blizzard," Ebbert said of the challenges Blizzard has faced creating the game.

"What we showed at the original BlizzCon, we've completely flattened it since then and completely rebooted it because we just thought, there's more we can question on this.

"Outside of that I really can't dive into details."

Going slightly further, Executive Vice President, Product Development and Co-Founder Frank Pearce explained that Blizzard hopes to make its DOTA mod more accessible to newcomers.

"One of the important things to note with that space is the DOTA everyone plays on Warcraft 3 is not particularly accessible to the novice," he said. "One of the game development philosophies we have at Blizzard is, easy to learn and difficult to master. That mod for Warcraft 3 doesn't really fit that description.

"That's a big challenge for us: taking this concept that doesn't really fit that philosophy and adapting it to a philosophy that's important for us."

Ebbert agreed: "DOTA's a very addictive game that chases the vast majority of people off because their team mates are screaming at them. We've always felt DOTA has a very accessible, easy to approach fun game deep down inside that's just waiting to come out.

"We've just been basically carving around that and trying to knock off all the rough edges and really make it more user friendly."

More details on Blizzard DOTA are expected at BlizzCon later this year. Valve's competing effort, DOTA 2, debuted at Gamescom last week and is due to launch next year.