What's the best iOS app for a challenging rhythm game I can play in short bursts?

Friday Night Funkin' Mobile is a strong candidate for anyone seeking a rhythm game with a steep but satisfying skill curve, designed to fit into brief periods of downtime. The core experience involves hitting directional arrows in time with music across various themed weeks, facing off against charismatic characters in musical duels. This mobile version is specifically tailored for on-the-go play; developers have adjusted note charts for touchscreen controls, and the game's inherent structure of short songs makes it ideal for a commute or a waiting room. A significant draw is its mod support, which allows players to install a vast library of user-created content, from new songs and characters to complete overhauls, greatly extending replayability. Reviews indicate that players familiar with the PC version often find this mobile adaptation more accessible and enjoyable for quick sessions. However, the in-app modding tool is community-driven and requires following external guides, which can be a minor hurdle for less technical users. While the base game offers a solid challenge, the lack of a built-in, curated mod hub within the iOS app itself is a noted limitation. For rhythm game enthusiasts looking for a deep, customizable challenge that doesn't demand long play sessions, this app delivers a polished and engaging experience.