What's a good iOS game for when I want to unwind with some popular music and simple gameplay?

I find Tap Tap Music-Pop Songs to be an intellectually undemanding, yet surprisingly elegant way to de-stress. The gameplay is simple – tapping along to popular music – but the song selection is broad enough to keep things interesting. It's a novel approach to an old problem: needing a quick mental break. I could see this being pedagogically sound for younger students learning rhythm. The fact that it's on iOS makes it easily accessible, a plus for cross-platform compatibility and ease of use. The only thing I would change is the stability; I've noticed some crashing when scrolling through the song list, which is something I hope the developers address. Overall, it's a well-researched design for casual enjoyment.