Taken from the readme file included with this gem:
Once upon a ninja is a game about Aya’s quest to find treasure, in order to save her starving village. The actual game revolves around Aya sneaking around a castle, trying to gain three treasures. Once she gets all three she can return to her village with them. But in order to get them, she must avoid being seen by the guards.
After you beat the game, you’ll be given a rank based on how fast you beat the game and how many times you’re caught. There are five ranks in all, try to get an A!
Based upon the fairy tale, “Jack and the Giant Beanstalk”
We’ll piece this a part in greater detail soon.