Some games are undeniable classics. Noughts and Crosses, Tic-Tac-Toe, Connect 4, Four in a Line - whatever you happen to call the line-em-up game - there's a smart little app called Tic Stac Toe which adds a third dimension to the game. As if a flat, two-dimensional board wasn't taxing enough, this app will have your brain thinking in all possible directions.Tic Stac Toe\nFormat\niOS\nPrice\nFree | \u00a30.69 for full, unlocked app\nWhere\niTunes\nThe goal of the game is to create a board-length line of your own colour\/shape counters. It's as simple as that. Problem is, the turn-based set-up means that an opposing player's counter placement can, er, counter your plans of success.Play alone against computer artificial intelligence, pass and play with someone in the same room, or set up an account, log in and play online against friends - there are plenty of options.In three dimensions there are lots of possibilities to create a winning line: think about stacking counters on top of others for diagonal lines that either lie flat or rise vertically through any three-dimensional direction.\u00a0With so many blocks stacking up it can be tricky to see your opponent's line of attack. Here's where a single finger to the smart device's screen will help navigate the in-game camera to get a tailored, prefered view of the board. Pinch-to-resize can also come in handy.In the free version of Tic Stac Toe - which is the no-frills version - there are 3x3 and 4x4 grid sizes with easy and medium difficulty computer AI settings, whereas the pay-for app adds in a 5x5 grid and a hard difficulty setting.We found that even on medium difficulty the computer would frequently ruin us multiple games to one, although it can be scatty too, as occasionally it would leave obvious wins wide open a mere handful of moves into a game.The free app is also stripped back to the bare essentials: the gameplay is all here, but there aren't different counter shapes and multiple backgrounds which can be unlocked or puchased via coins in the app's store. For that you can either earn coins against competitors online or buy them outright. We were happy enough just playing on the basic table without any background distractions.\u00a0That's all there is to it. A fun way to pass the time, although occasionally inaccurate counter placement will have you swearing at the screen.