This game has one of the best shop systems Ive ever seen in an iOS game, and its very addicting to play. Even though the gameplay is honestly somewhat repetitive (as it would be) I can tell a lot pf work was put into making a diverse environment, such as different kinds of obstacles and even different biomes (which dont really affect the game, but help heighten the mood). I found it to be a little too "pay-to-win" with characters that were kind of cheaply designed and didnt have much depth and the characters you had to buy were always better. As with all iOS games, there were things about it I found stupid, but it gives you a good 6 hours of gameplay, Id say, before it gets boring.
Smithersink about Rail Rush, v1.9.10