A code kata is an exercise in programming which helps a programmer hone their skills through practice and repetition. The term was probably first coined by Dave Thomas, co-author of the book The Pragmatic Programmer, in a bow to the Japanese concept of kata in the martial arts. As of October 2011, Dave Thomas has published 21 different katas.
The game consists of 10 frames. In each frame the player has two opportunities to knock down 10 pins. The score for the frame is the total number of pins knocked down, plus bonuses for strikes and spares.
A spare is when the player knocks down all 10 pins in two tries. The bonus for that frame is the number of pins knocked down by the next roll.
A strike is when the player knocks down all 10 pins on his first try. The bonus for that frame is the value of the next two balls rolled.
In the tenth frame a player who rolls a spare or strike is allowed to roll the extra balls to complete the frame. However no more than three balls can be rolled in tenth frame.
http://butunclebob.com/ArticleS.UncleBob.TheBowlingGameKata
http://angeleah.com/blog/2012/07/05/tutorial---the-bowling-game-kata-in-ruby.html
The implementation took me about 6 hours (13 pomodoros) of working time from start and this commit