OK I got The Idolm@ster Platinum Stars for PS4 via Play-Asia. Wow. It takes some getting used to but the game is incredibly sweet and the songs, while not too many yet, are fun. Happy is especially fun. The game features music rhythm games where one earns EXP and money, mini games where one can power up the idol in terms of say fan numbers, and even a " Stage for you " section where you can have the girls perform each song for you, and you can co-ordinate the outfits. In between these things are cut scenes with girls interacting with you in Japanese, and it is possible to use phone based translation software to figure out what they're saying beyond "good luck" or "happy birthday".
The game has no negative elements. There are no panty shots or any lewd fan service. Everyone is pure and chaste, and each girl has her own story to tell -- which may or may not follow the official anime (available on Crunchyroll). Anyway one can have a group of 3 idols with the leader getting most points per song, and every so many songs there is a medley where all girls perform. Each performance is rated and matched to your equipment = each outfit and accessory has level ratings and improves stats. With better equipment one need not be so good at pressing the buttons to time with the music. However some stages do require lots of leveling up because even perfect scores do not clearing.
Unlike Hatsune Miku Project Diva games the voices used in these songs are mixed in game, and are real voices. The songs also don't end if you don't do too well, and you score points for even songs you did not clear which translate into EXP. The music rhythm games are also easier. For example I found myself not being able to play on Normal on Project Diva while on Platinum Stars I am able to play PRO or MASTER (the hardest difficulty) on most songs.
I would hope Namco translates this game into English, and seeing how many fanservice Japanese games are making it Westward, it's really a pity that an innocent game such as this one can't make it. Still it is worth playing and I think it's a game the whole family could enjoy - although the cute aspect of the girls may put many people off. Still as said there is no questionable stuff in the game. Namco has translated this game into Chinese and Korean, but sadly no English subtitles. And it would not be a hard thing to do.