The gameplay of Radiohammer is basically to tap the screen at the right time to hit a person/object coming towards your character at the right time. Taps are accurate which results in tight gameplay.
Cytus has a simple, easy to understand gameplay - you tap, longpress or drag one of only 3 types of bubbles when the line crosses over them, but it quickly gets a lot more difficult when the number of bubbles on screen starts to increase. To master the game, you have to memorize the songs and be prepared to practice.