I can never work out whether to call this game 'Othello' or 'Reversi', but either way it's a fun way of passing some time that has always translated well on portable devices.
This free version is a faithful incarnation of the original that includes some interesting options to keep you amused for some time.
In case you don't know, the game is played on a 8x8-square board, with players alternating with the computer using black and white stones.
The objective is to form your coloured counters around the opponent's in order to 'capture' them and turn the stone into your colour. The player with the most stones at the end of the game is declared the winner.
CEZebra boasts different difficulty levels, the highest of which is very, very difficult. There's a neat practice mode though to help you fine-tune your skills before you take on the might of the computer opponent.