iStar Drummer HD is a music rhythm game in the style of Guitar Hero. It provides a virtual six-piece drumset with customizable keyboard mappings. The player can select from Story Mode ("Star Road") or Arcade Mode ("Music World"; additional charges apply); the goal in either is to accurately produce the beats portrayed by falling colored symbols, theoretically in time with the background music.
The problem is that, as nice as some of the music is, it just doesn't line up properly to the beats you're forced to play. Pressing keys in time with the music will almost invariably result in a loss. To succeed, one has to either mute the audio and imagine the rhythm behind the keypresses, or else madly spam relevant buttons whenever a symbol gets close, since there is no penalty for keypresses in the absence of a symbol.
The game has promise. But between the lack of sync and the unrealistic per-track in-app purchases for Arcade Mode, it's not yet worth playing, let alone buying.
Sam's Protip: If you like the music, take a look at the app's package contents.