Not all Zynga's games are free-to-play.

Drop7, Chess With Friends and Words With Friends are some of the handful of paid games the social publisher has available.

It's perhaps more surprising that the new release from Zynga Mobile Germany (previously Gamedoctors) is being offered in this way, though.

A brand new game from the studio that Zynga acquired in October 2011, Zombie Swipeout has just been released in Canada for beta test purposes, and is available in an ad-supported free version, and a 99c paid version.

Added extras

Of course, there are plenty of hooks to encourage players to shell out for in-app purchases.

The Fruit Ninja inspired title has many bats, swords, knives etc to purchase using in-game currency. There's also a rescue option should you slice a good guy rather than a zombie, triggering a 'game over' condition.

Another controlling mechanism is the energy system, which limits how many game sessions you can play. Total recharge takes around an hour or you can drop currency to buy more energy.

Traditionally, players have reacted badly to such obstacles - remember ngmoco's Eliminate? - so it will certainly be interesting to see the feedback.

We'll also be looking to see the comparative chart positions of the free and paid versions in the top grossing charts, following the no doubt imminent global release.