No one asked Vicarious Visions to make Guitar Hero for the Nintendo DS. No one at studio owner Activision, fellow Activision subsidiary RedOctane, or Nintendo believed it was even possible.

"People thought it was ludicrous," Vicarious CEO Karthik Bala told me at a Guitar Hero event earlier this week. "It was never in the plan to do that."

As Bala puts it, the whole thing came out of the Vicarious staff playing around to "see if it was even possible to do a really good music rhythm game on a handheld." Twenty-three prototypes and a few cardboard guitars later, a breakthrough came in the form of a "crazy Frankenstein GBA cartridge" wired with fret buttons.

Activision and RedOctane thought it was insane. And when the first prototype was presented to Nintendo, Bala says they were stunned.

But the really, really amazing part? For all the unwieldy-looking peripherals and wacky ads, the Nintendo DS entry, Guitar Hero: On Tour, really is Guitar Hero. It works. It's fun. In fact, I think it does some things better than the console editions of Guitar Hero 3. Registered users can use the HD Stream.

The second that No Doubt's "Spiderwebs" started playing, it didn't matter that my hand was curled around a DS instead of an actual toy plastic guitar. The part where I was about to strum the touch screen with a pick stylus didn't factor in. And I didn't miss a note, at least at first, which surprised the hell out of me. I wasn't expecting the transition to be that seamless.

Whammies? A simple matter of holding down the stylus and shaking it back and forth. Star Power? Yell in the mic, or just press one of the face buttons during a slow bit.

I wasn't expecting the game to be so challenging either. Don't get me wrong, I'm no master, but I can get by in Rock Band and Guitar Hero on Expert. However, the second I tried anything beyond Medium in On Tour, I didn't do that well. So much for the missing button making the game easier.

Don't be fooled: While On Tour seems pretty pick-up-and-play friendly, it sports the same kind of learning curve and nuances as the console editions. Simple strums will suffice in the early songs and lower difficulties, but to advance in the higher tiers, you have to learn to be more efficient with your strumming.

In the console versions, this can be accomplished by strumming up and down instead of just down. On the DS edition, I found myself instinctively lifting the pick away after each strum. I had to retrain myself to keep it low to the screen, to alternate left and right strums instead of going in one direction. I still didn't do all that well, but I got further in Blink 182's "All the Small Things" than I did on an earlier attempt.

But where the game really shines, and where I feel it surpasses Guitar Hero 3, is in its item-based Duel Mode. You can face off against an actual opponent via local wireless or duke it out with an AI character, and as with Guitar Hero 3, you earn items by hitting all the notes in a certain combo.

This time around though, the item-based attacks are more fun than frustrating, with skill and reflex playing a larger role than luck and patience. A broken string doesn't force you to stop and endlessly mash a fret; instead, you can quickly restring it with the touch screen. The temporary screen swap will probably have you attempting to strum on the top screen of the DS, but most will learn to compensate on the fly.

Amp fires can be put out by blowing on the DS instead of waiting for them to extinguish on their own. And, really, who's going to get that angry when they have to briefly stop playing to sign an autograph?

If you want definitive proof though, here's the telltale sign that there is fun to be had. In a room full of jaded and experienced game journalists, no one was talking. Everyone had their headphones on, completely engrossed in the game. As I put the DS down, the only sound I could hear was the gentle "tap tap tap" of nearly a dozen plastic picks.

Amidst the frequent tapping, I was able to catch up with the developer's CEO, who filled me in on some of the more interesting aspects of the title's unorthodox origins.

Shack: How did you adapt the note charts for the GH3 tracks from five to four buttons?

Karthik Bala: We actually did all the note charting from scratch for this game.

We knew we had to note chart everything from scratch anyway because the timing of using the guitar pick stylus on the touch screen is different than the timing of the strum bar on a guitar.

When we selected the songs that we wanted to bring over from Guitar Hero 3, they were remastered for the best audio fidelity on the DS and they were re-note charted and scaled. We still have Expert as really friggin' challenging, as you noticed, and it scales really nicely from Easy to Expert.

Turn the page for more, including a partial track list, talk of early prototypes, and Nintendo's reaction to the project.