Unless I'm not reading this right, there is a DSiware version coming with all of the extra features of the retail version, plus another extra mode. And it's obviously going to be cheaper.
DSi owners can get down on the DSiWare version, which PopCap says is coming in the next several weeks. It will have the four bonus modes of the DS version plus one more called Zombie Trap. Personally I am not buying another version of that game as I found it to be quite overrated in the first place, but for those with DSi's planning to get the game, I thought you'd like the warning.
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