The game consists of four rounds. In each a square of 44 is created from the sixteen face up tiles. Once the round is completed and scored the next set of sixteen tiles are turned over. The clever aspect here is that all four colours are equally represented on the tiles in total but are randomly distributed both on individual tiles and over the groups of sixteen in each round. Thus in at least one of the rounds you may have very few tiles of your colour represented.
Each turn consists of playing one tile, containing your own colour, to the playing area adjacent to one already down. Your colours must be linked together, if possible, by their adjoining walls. By this means a 4 x 4 grid is gradually built up. On completion, scoring for this round occurs. You may choose one connected line of towers of your colour and score one point for each tower in the line multiplied by the number of edges reached by this network. An incredibly long network which connects no edges would score zero points whereas one reaching all four sides would be multiplied by four. This continues over four rounds and the highest total wins.
The whole game system is very simple in concept but works extremely well in practice. One favourite tactic is to use tiles which have both your colour represented and also several towers of an opponent. These may be placed so as to optimise your own network whilst isolating the opposition. As the grid is built up in play it is also possible in the mid game to manipulate which tiles form the edges and hence the greatest chance of picking up a high score.
The two player version is my favourite and also the most intense but the system is versatile enough to accommodate four with relative ease and still retain a fair degree of tension.
The game looks colourful, plays well and has constant interaction. Another recommended item!