The boss battles in superb science fiction action role-playing game Deus Ex: Human Revolution were not developed by Eidos Montreal.
Instead they were outsourced to little known studio Grip Entertainment.
Deus Ex's boss battles drew criticism for their frustrating difficulty spikes. They also focused on action gameplay when much of the game encouraged the player to use stealth skills.
In a video posted online, below, Grip boss Paul Kruszewski admitted creating the boss battles was a tough job.
"Full confession: I'm a shooter guy," he said. "I was coming into this not knowing a lot about the Deus Ex world.
"The guys at Eidos gave us the design, gave us the engine. We brought in our own behaviour tree engine and we gave them back that experience.
"Boss battles are special moments. There were two challenges: we had to take our tech and inject it into the DEX3 engine. And then within DEX3 itself is, you're coming at it, and you can be anybody, you can have this augmentation, that augmentation, this weapon…
"And so, balancing all this stuff, you don't know the priority of the guy is coming into the game, and you want to give him a great experience. You want to be true to the designer's vision, but you want to give the player a great experience. So balancing was brutally hard."
But Kruszewski had a word of advice for players struggling with Deus Ex's boss battles.
"There is a flow to these guys. We think there is a lot of fun. You've got to figure out what their OODA loop is. You've got to get in that and it's going to work out.
"But if you panic, you're going to die. Simple as that. So just remain calm. Be Zen, and orient, observe, decide and act."
Despite the divisive nature of Deus Ex's boss battles, the game was critically acclaimed upon its launch, and shipped two million units within two weeks.