Rush Hour is a fun game that engages your brain just enough to be difficult, but doesn't tax you so much in the beginning that you get frustrated. Actually, it's pretty addictive, especially on the easy levels. The game's premise is simple: the player has to get the red car to the Exit ramp, but there are a bunch of other vehicles in the way. You move the pieces until the path is clear. The cars can only move left/right or up/down in their lanes. The higher the level, the more cars and more jammed up the traffic. There are multiple ways to solve each puzzle, but a further challenge comes in solving it in the fewest moves. Each level has a Perfect score to reach for. The scoreboard will keep track of which puzzles you've solved, your highest score, and any perfect scores you attain. Players can either move through each board in order or pick any challenge they want to try or go back to.
The company behind the game, ThinkFun, has actually been making portable games (in the physical space) for several years. A year ago they started remaking the games as apps without needing to change the premise or gameplay at all. The only difference is that, in app form, they can include more challenges plus Hint and Solve features.
Rush Hour has both free and paid versions for Android and iOS. The free version comes with 35 challenges -- 10 each for Easy, Medium and Hard, 5 for Expert. The full version -- $1.99 on Android and $2.99 for iPhone/iPad -- has 2,500 challenges, so you won't get bored for a long, long time. Find Rush Hour and Rush Hour Free in Apple's App Store and on the Android Market.