Zombies.io

This is an intense, solo survival roguelike played in short, interruptible sessions, likely in portrait mode. While it offers high replayability and can be played offline one-handed, its difficulty is extremely high, with some users reporting pay-to-win mechanics and unfair progression that can lead to frustration. It's best suited for players who enjoy challenging, fast-paced action and don't mind a steep learning curve or potentially unfair monetization.