DoDo - Game "24" with extras

DoDo (the abbreviation of DOuble DOzen) is an implementation of card game "Twenty Four" (24), popular in China and other countries with significant Chinese population, including Australia. The objective is very simple: to compose 24 out of four numbers, each in the range 1-10, using four arithmetic operations. A player who does it more often wins the game. As opposed to majority of other intelligent card games, game "24" does not involve any hidden information therefore there is practically no need to remember cards or apply any long-term strategy, while fast counting is the only prerequisite to succeed. That makes "24" an ideal family game which helps to development arithmetic skills for primary school children and provides entertainment for adults at the same time. Incidentally Dodo is a name of the bird species unique to tiny island Mauritius to the East of Africa. Dodo birds peacefully lived, eating fruits and nuts falling from trees. They didn't have any predators apart from human settlers who eventually led them to extinction in the late 17th century. Fortunately, some illustrations, descriptions as well as remains of the birds have come to us. Dodo was the nickname of prominent English mathematician and writer Charles L. Dodgson, better known by his pen name Lewis Carroll, who invented a number of brain-teasing games, like a sort of "Scrabble" and still popular "Doublets" a.k.a. "World Links" or "World Ladder"). In his most famous novel "Alice in Wonderland" ,Dodo bird represents the author himself and, just like the author, invents a game. —————————————— This version of game "24" encourages fast thinking. The score depends not only on the number of solved puzzles but also on the time spent on solving. If a combination has no solution, a player who figured that out is rewarded as if the puzzle is solved. DoDo currently supports playing against the computer or another human player with one or two packs of cards. The application also provides training mode which can be made void of time limit and allows to enter your own combination for the computer to solve it. Different extensions to the game rules are available. For example, you may allow Ace (One) to stand for either one or eleven in order to enlarge the variety of solvable combinations, so, for inastance, "A A 2 3" gets a solution: 11×2+3-1. Other available options are common fractions, exponentiation (raising to power), "merge" operation (writing one number after another) and presence of Zero card (Joker). Even "magic number" 24 can be changed to a different value! DoDo provides a variety of customized features. In particular, a computer solution can be presented either as sequence of operations (e.g. 6×3=18; 3×2=6; 18+6=24) or as an expression (6×3+3×2). Other customized features include choice of background texture and color, replacing standard playing card images by numbers, different types of animation. The application supports sound effects and also can play custom background music, specified as an album or a playlist. Both portrait and landscape screen orientations are supported and the orientation can be changed "on fly". DoDo allows to save unlimited number of games. The application keeps local tables of scores and achievements. In addition the achievements, as well as results of a quick game can be published at global tables provided by Google Play Services. The application is designed to adapt to any version of Android. 'Vintage' release, available for Android pre 4.0 is free of limitations, however does not have access to global tables.