It's still a couple of weeks before the Angry Birds kart racing game hits mobile devices in North America, but it's on New Zealand's iTunes right now, and I've played it long enough to get very angry with it. Energy meters? Really?

A lot of folks like to rip on the Angry Birds series for releasing the same sort of game over and over again — generally folks who don't play those games. Tweaking the established formula is almost as much a hallmark of developer Rovio as providing regular doses of free content long after its games are released — the original Angry Birds got a new free update just this week.

Rovio has also done a good job of steering clear of free-to-play mobile pitfalls. There are microtransactions, but they're generally limited to purely optional power-ups, which are never necessary to complete a level.

I have a pretty high opinion of the developer, which is why what it's doing with Angry Birds Go! has me so puzzled. Energy meters, limiting the amount of time folks can play? Souped-up cars for cash? And all of this done in a game that's riddled with corporate sponsorship?

It's shaken my faith, to be sure. I always thought of Rovio as one of the good guys.

Angry Birds Go! is due out on December 11, so chances are the version I played from New Zealand's iTunes is largely the same one we're getting here. It's quite pretty, and it handles nicely, but the first time I run out of energy and have to wait for it to refill is the last time I am playing.