If John Carmack is id Software's mad scientist, then Doom: Resurrection is his latest experiment. Developed largely by id/Ritual veteran Tom Mustaine and his team at Escalation Studios, Resurrection is a rail shooter take on Doom 3, priced at the premium rate of $10.

With the launch of the game today, I sat down with Carmack and Mustaine to talk about the risky project. Also covered are Carmack's criticism of the iPhone's current shortcomings, his take on how the ZeniMax acquisition will affect his time to develop pet projects, and what's coming next from id Mobile.

Tom Mustaine: Did you get a chance to install and play the game at all?

Shack: I did play it a little bit, yeah.

Tom Mustaine: Cool, so you can see that we've kind of taken a different approach to traditional shooter, Doom stuff. How far did you get?

Shack: I want to say about 40 minutes? I played mostly on a subway--not the best tilt-control environment.

Tom Mustaine: [laughs]

Shack: The controls are interesting though. It's a clever scheme. How much work went into figuring that out?

Tom Mustaine: It's interesting. We actually started developing the game about eight-nine months ago. We knew we were going to go for a crafted, pull-you-through-the-world experience, and that's what best fit the devices.

Initially we kind of looked at the Apple devices and said the best controls to do with this would have been touch screen. And we had a solution for it where you could touch on the screen and shoot the monsters in a very similar way you'd expect with most of the other stuff that's come out on the device. And basically we got about halfway through the project and we just weren't having any fun. Visually it looked great, technically we had solved all the goals we wanted to solve, but it just wasn't any fun at all tapping the monsters. Basically, tapping on the screen, you're covering the monster, you don't see the blood, you kind of miss all those core elements.

So we made a pretty big change. At the halfway point of the project we were kind of considering, this could get canceled if it doesn't get fun. And so we moved it over to the accelerometer controls, and it was kind of surprising, because I think we've played almost every other game called a shooter on the iPhone, and nobody's really landed on this control mechanism before. And that was kind of our "ah-ha" moment.

The goal was to capture the visceral Doom experience down to the iPhone, so we've got shooting, dodging, covering and reloading, all the things you expect in a traditional shooter. And then you get the aiming mechanic in there, and you have that core microsecond compulsion where you're taking aim, you don't know if you're going to get killed by this guy, and it actually really kind of gelled together and became the right ingredient for this title.

John Carmack: From the beginning we were looking at this as an experiment. We obviously know we can do a great job with traditional FPS on a traditional platform, but when you're looking at something that's really different, I was looking at this like my original foray into mobile with Doom RPG. It's a different platform, and we can't do the same type of game that we've been doing, so what do we do from scratch here?

And the fact that we were fully prepared--literally, it did reach a point where I thought I was going to cancel the project, because it just wasn't coming out that fun. And even though we had pumped a not-inconsiderable amount of money into it, we weren't going to release something that wasn't any good. We were expecting this to be our best, first foot forward on the iPhone platform.

In the end, things did sort of work out that way, in that I did the Wolfenstein 3D Classic sort of on a lark, and it turned out more fun than I expected, and we did turn that into a product ahead of our strategized pace. But it'll all turn out well in the end. I think that that turned out to be a pretty good first foot forward there, and this is sort of bringing around one of the big guns for us.

Shack: The graphics are also rather impressive for an iPhone game.

John Carmack: We are cutting a whole lot of corners. There are smoke and mirrors going on here. People look over their shoulders and go, "Holy cow, it's Doom 3 on the iPhone!" But it's really not. It's pretty much old-school game design where we are cheating so much, but in ways you can't really see.

It probably would be possible to do it on the 3GS, to do a more free-roaming game like this with similar visuals, but this is most of what can be accomplished on the first-generation phones. There are a lot of things that we hide very well in the current presentation, but there are no rockets in the game because there really isn't a collision system. The lighting is set up for only specific things happening. We made all the trades to get the type of experience we were aiming for here.

And yeah, it could definitely be faster. I did some performance analysis at the end and we looked at all of this and said well, this is about as good as we're going to get in the time that we've got available. If I wanted to go back and do everything from scratch right now we could do better, but that's true of every single title I've ever done in my life.

Tom Mustaine: Yeah, and basically we targeted--there's a significant speed difference between the first gen iPod, all the way up to the 3G phones, and then also the second gen iPod Touch is then also the fastest device up to the 3GS.

We targeted all of those devices, and you get a good framerate on all of them. And like John said, we pulled some good tricks, specifically there's actually a custom visibility solution in there based on some stuff that John's team did with Rage. So we actually have some really crafted, cool stuff in there to make sure it's fast on every device.