The American Dental Association and Popcap have teamed up to provide free game codes for anyone who wants to download Plants vs Zombies–but there’s a catch. You have to redeem these codes on Halloween or the week afterward, or the coupon code is lost forever. Parents are encouraged to share these coupon treats instead of sugary ones this Halloween to cut back on tooth decay without getting rid of Halloween’s holiday spirit. Dentists have been given limited-edition trading cards to give to their patients, but anyone of any age can join in on the fun by downloading and printing a set of coupons on StopZombieMouth.com .

In case you’ve never heard of Plants vs Zombies, the game itself is similar to defense tower games, but it gives you lanes to defend instead of a wide area, and you use plants instead of strange contraptions. There are 30 different plants to choose from, and all of them do different things. Combining the different plants to defend your house (and your brains) is more challenging than it looks, and you have to do all that while protecting a line of sunflowers as well. It also features twenty different minigames as well as a puzzle mode, so if tower defense isn’t your thing, you should still take a lot of the game.

The partnership of the American Dental Association and Popcap is definitely one I didn’t see coming, but given how addicting the game is, I’m glad I can finally give my friends a free copy of the game. Whether the game will be activated on Steam or a direct download from the StopZombieMouth site is still a mystery, but either way, I’m sure the game will be compatible with multiplayer. If you happen to be going to a Halloween party later this year, make sure to print out these cards and impress your friends (because, you know, Plants vs Zombies beats out stale candy corn any day).