Warning: This game is ADDICTING! By far the best rhythm game I've ever played. The gameplay is customizable with choices of difficulty and speed of how fast the notes are. It's simple and fun, but also can take skill. You can play casually, or hardcore, either way you will be satisfied. The selection of music is large and is constantly growing, and rotating, so you don't have to pay to play the music, though I do pay to unlock more permanently. All the songs in my opinion are catchy and really nice to listen to, that's right, ALL OF THEM! I don't think I'll like a song, then I play it a few times, and I end up really liking them. One of the weaker points is probably the story, while nice isn't really necessary in my opinion. Also to be noted you will need wifi to play the game, so it's harder to play it on the go, and I recommend it more for phones than tablets, because it is harder to use on a tablet. But still, it's definitely my favorite app! I definitely recommend it. If you don't think you'll like it at least try it, I mean it is a free app.Edit: The key system is becoming a problem. It’s going to cost you some money if you want a good selection of songs. If you have a Nintendo Switch, I’d recommend you get it there. It’ll cost $25 USD, but you get all of the songs, so if you wanted to pay for more songs, this is a good option.