Nintendo DS, 2010
Beat City is the game I play in between everything else. It's possible to enjoy it in very brief sessions, and I'd actually argue the game is better when played only occasionally. In the end, there are not that many different stages so there's always the risk of things getting repetitive if you play for too long. I'm now somewhere around halfway through (though this is a rough estimate) so the game could throw in some surprises still.
With that said, I must confess to really liking Beat City. Hands down the best western rhythm game I've played that isn't centered around guitar-shaped peripherals. I'd even go as far as to say it manages to challenge my all-time favourite DS rhythm title Osu! Tatakae! Ouendan!, though O!T!O! still remains the reigning champion.
So far Beat City has had a catchy and upbeat chiptunesque soundtrack, decent gameplay and a charming visual style. My only complaints are the somewhat illogical way tutorials are handled, and the slightly repetitive stages.
(If you're wondering what Playing for Time is, see this explanatory post.)