After the "Angry Birds" phenomenon, "Flappy Bird" is spreading its wings to every smartphone and becoming the most downloaded free iPhone and Android app in the past weeks. The app was developed in Hanoi, Vietnam, by Nguyễn Hà Đông, or better known as Dong Nguyen, and had it published under independent game developer .GEARS Studios.

Launched in May 2013, the success of "Flappy Bird" has been called "sheer luck." It became an overnight success after a wave of tweets from addictive users, YouTube videos and reviews in iTunes and Google Play. "Flappy Bird" developer said that he never did any promotion for the app and revealed in a recent interview that the app's popularity is just his luck.

Here are five amazing things to know about "Flappy Bird," "The New Angry Birds."

1. An annoyingly addictive mobile game, "Flappy Bird" is generating $50,000 in sales per day, according to The Verge. The game generates revenue through banner ads. In January 2014, the app topped the American and Chinese iTunes App Stores in its free category. It also topped the UK App Store where it was dubbed as "the new Angry Birds."

2. A no-frills smartphone game, "Flappy Bird" fluttered its wings all the way to the top, but its popularity still remains a mystery. Its addictiveness is contagious and its absurd level of difficulty has driven many users to the brink of madness. The game is pretty simple yet it spawned thousands of online rants and hysterical reviews which made others download it because of curiosity. Paul Tassi of Forbes wonders about this phenomenon and said, "What does that say about society as a whole? Have we reached a level of boredom bordering on dangerous if we're spending our time en masse on something so pointless?"

3. The simple idea of "Flappy Bird" comes from a Vietnamese developer who surprised the world when he beat the likes of Supercell ("Clash of Clans") and Rovio ("Angry Birds"). What makes it interesting is that he didn't have any lessons that these big guys have. "Flappy Bird" doesn't have multiple levels. It doesn't make players buy packages for more levels but allows users to share and rate via a three-point star system. Having no big shot apps is the key reason why people from all walks of life are addicted to the game.

4. Although many are saying that the game is a fluke, Dong Nguyen managed to deliver what people need and want for casual gaming. "Flappy Bird" is not his one-time hit; he has two other games ("Super Ball Juggling" and "Shuriken Block") that are included into the top ten of the App Store.

5. Dong Nguyen is also brewing new games on his Web site which are not featured in the App Store such as "Smashing Kitty," "Ninja Assault" and "Droplet Shuffle." All these apps can be played on any smartphone.