The evolution of the slot machine industry from computerised machines to video slots and the increasing popularity of online casinos and mobile gambling open a world of opportunities for game designers to develop new types of game routines. In this new setting the potential of increased, even unlimited, player interaction arises. Game designers must embrace the change and develop innovative games that make the most of it. Attractive game ideas are needed that will catch the interest of the players by offering them new and exciting possibilities, yet not too new and different that the players are alienated. Succeeding in attracting player attention and interest is important because of the size of the industry. In the UK, for example, gambling makes a significant contribution to the economy with an estimated expenditure of '8,875 million (0.8% of UK GDP (Gambling Act, 2005)), of which '1.74 billion is made in costumer losses playing slot machines (Gaming Board, 2005).

Slot machine games need a corresponding mathematical model to make sure the game is profitable and to accurately calculate the minimum house edge. In those games that the player has an input, the player's optimal strategy must be calculated in order to calculate the minimum house edge. Probability, Operational Research techniques and Stochastic Processes are used to build these models. Good programming skills are also necessary. If video slots are to allow games to be more interactive these games could become more sophisticated and, consequently, more difficult to model. This is a specialised job that only well trained professionals can do.