Mark of the Ninja snuck out of nowhere to emerge as one of the best downloadable games of 2012. We asked Klei Entertainment’s lead designer Nels Anderson about how the game came together.

Game Informer: Thanks for taking time to answer our questions. The studio’s previous work with Shank was rooted in the action vibe. What made you excited about making the switch to a stealth focus?

Well, not a lot of folks know this, but Klei's first game was a physics-based puzzle game called Eets. It's sort of like The Incredible Machine but with crazy cartoons instead. So going from that to Shank was already a bit of a change-up (and we're actually doing a new version of Eets that will include iPad, which is like the perfect platform for the game, so folks can look for that soon-ish).

Also, I didn't actually work on Shank or Shank 2, really. I did maybe a month of level concepts for Shank 2, but I basically came back to Klei for Mark of the Ninja. So it wasn't a big switch for me. I've always really enjoyed stealth games, so it was more or less the ideal game to design.

And the rest of the team was very excited to be doing something new as well. We didn't want to get pigeonholed as "the 2D brawler studio." There was a lot of things we learned from Shank that we could carry forward of course, but everyone was very excited about the change of pace.

Anderson: Are there any particular inspirations – in games or other mediums –  that you looked to when crafting the game?

In terms of games, Thief was a big one for me, both as a designer in general and for Ninja in particular. The emphasis on systems, player choices and pacing was something we tried to evoke in Ninja. Other stealth games were of course influential.

In terms of the narrative/theme, that's a bit tricky since nearly everything that's about ninja in pop culture is either hyperviolent, totally cornball or both. More grounded spy films, like the Bourne movies, was closer to what we wanted tonally. We also drew on real Japanese history a lot, as well. I'm a giant history nerd, so Ninja's writer, Chris Dahlen, and I dug into moments from Japan's warring states period where actual ninja operated for some moments in the game. It's pretty subtle, but most the references to the past made in the game are references to things to actually happened. One mission starts with Ora, your companion, mentioning Sawayama Castle, which is a castle that was burned down after ninja infiltrated it and set it on fire.

How did Mark of the Ninja change over the course of development? Were there features or elements of the game that you dropped or added as you shaped the game?

The initial experience we wanted to provide was pretty much exactly what we ended up with, but the way we got there definitely had a lot of changes. The whole sound visualization stuff, for instance, wasn't something we imagine in the first design write-up I ever did or anything like that. It was something that evolved organically over the course of developing the game. But the reasons why it came out, the focus on player choice and multiple valid approaches, was there from the onset.

We experimented with a lot of different mechanics along the way. But it was all basically driven by getting closer to the experience we wanted to deliver. We experimented with probably like three different combat systems along the way, but all of them dragging us further away from the stealthy, considered, observational gameplay we wanted to provide. The focus was all about experimentation and iteration though, there wasn't anything sacred that we had to keep or simply couldn't be added.

Mark of the Ninja offers a cool twist in its conclusion that ties back to the earlier parts of the game. Was that element a part of the story from the beginning?

The initial structural notion of the game was actually about having a lot of much smaller levels, like 60 or 70 levels over the course of six worlds or so. We discovered that the levels we tried to build in that fashion weren't very enjoyable though. Eventually we ended up taking the very rough plot from one world (PMC CEO as antagonist) and expand it out. The worlds Ninja takes place is are roughly pulled from four of those original six potential worlds.

From there, I think it wasn't too long before we came up with the way the ending would shape up. We'd had themes we wanted to explore, tradition vs. modernity, trust and such, and so that felt like a good way to examine those themes.

[Next Up: What feature did Klei Entertainment take out of the game before launch?]