If you really like the Flappy Bird game, and subsequent copies, the you will like Crazy Upside Down Town Flying Taxi. It's very similar to Flappy Bird and is a lot of fun. You have to tap the taxi screen to keep the taxi flying. The goal is to navigate between two cities and avoid the blue buildings in both your world and the upside down world. The game's concept is simple but it does get addicting at times. I've found myself playing a lot longer than I initially thought I would. It's also great for killing time at work or home.