ZombiU developers were unsure if Survival mode were possible

ZombiU's Survival mode asks players to complete the entire game with just one player character, a challenge its developers weren't even certain was possible until the very last minute.

ZombiU normally allows players to respawn as a new character after death; their previous character becomes a zombie, and the new one benefits form all progress made so far in the persistant game world.

In Survival mode, there's only one character, so any mistake could lead to permadeath.

"The enemies aren't any stronger in this mode, but there were lots of times when the staff working on the development of the game were killed because they let their concentration slip for just a split second," producer Guillaume Brunier said in a new Iwata Asks.

"On the other hand, we made fine adjustments to ensure it was fair to you, so if a player loses a life, they only have themselves to blame. So, as we just discussed, they end up feeling inspired to do better next time."

"I think it must have been only two or three days before we finished work on the game before anyone made it all the way to the end," French studios general manager Xavier Poix revealed.

"In the bug database for Survival mode, someone had reported the funniest bug that I'd ever seen in all my life as a developer, saying that the game is too hard and can't be finished."

"Actually, the leaderboards will show when the first person completes the game Survival mode, so we'll know about it. I wonder how many people are up to the challenge," Brunier added.

ZombiU launches alongside the Wii U, so it's already available in the US and hits Europe on November 30.

The whole feature is pretty interesting reading thanks to Nintendo president Satoru Iwata's genuine interest in game design and how Ubisoft works; click through for plenty of discussion of the French company's history and the ZombiU project's development.