There's no doubt that the App Store is absolutely loaded with different physics games, and many with very similar gameplay to Tumbledrop [App Store], but few are anywhere near as cute, colorful, or filled with rainbows for that matter.
Gameplay amounts to making your way through the 60 included levels (with more coming soon per the iTunes description) by tapping on screen to remove pieces in order to guide the star at the top of the pile safely to the ground-- Very similar to game modes in the Topple series, Finger Physics, and others.
What interested me in Tumbledrop was the forced delay in between removing the pieces that comprise the various structures of each level. Other games you could pretty easily cheese your way through the challenges by just quickly removing pieces as fast as possible while guiding the goal item back to the ground. In Tumbledrop, you have to plan your movements carefully as you can only remove one piece every three seconds.
Tumbledrop isn't particularly original, but if you're a fan of these types of games you likely have several similar ones on your phone already. If you want to give the game a try, there's a free version you can play in a web browser, you just have to download the Unity browser plugin. It's worth a look, if only to see how happy the star you're rescuing gets when its on the ground accompanied by the fanfare of rainbows and multi-colored confetti before progressing to the next level.
App Store Link: Tumbledrop, $1.99