[daiidgo]

Congrats on the game guys, it's pretty cool. The federal registration on the Marble Drop name was dropped by Maxis back in 2004 (do a Tess2 search on the uspto.gov website). That doesn't mean that they've abandoned all rights to use the name for a mobile game... before you panic and change the name, or just shrug and ignore the coincidence, I would say go talk to a Trademark attorney. I'm sure you can find plenty of them up around MIT (most firms that do patent work will have one or two trademark guys). If you're going to continue to grow with your game, it'll be well worth the money.