LANGEN/PADERBORN -- Good computer games have much in common with successful feature films. They are not only top-quality entertainment; they also require a lot of effort to create.

Top computer game titles such as "Anno 1503" can eat up many million of dollars in research and development -- not to mention several years of time. Game developers also need a sort of script with which to work.

"The basic ideas are brought together in a written concept," explains Juergen Reusswig, managing director of game maker Sunflowers in Heusenstamm, Germany. His firm is the creative force behind "Anno 1503", DPA reported.

"This so-called game design document is similar to a script," Reusswig says. "It describes in great detail all of the game's situations, the game's mechanics, and the user controls," he adds. The game design document fosters the planning of the technical implementation, at which point the designers and programmers can get down to work.

A large part of the development time is spent on the so-called gaming engine. This central part of the program is responsible for the graphic depictions of the playing field, as well as for all necessary objects, such as houses, figures, plants, and animals, explains Reusswig.

Yet sometimes a lot of time passes before the script is ready. "It took us almost a year," remembers Daniel Vavra, a designer for the gaming firm Take 2. His company's action game "Mafia" won several awards last year. The game is set in the 30s. "We evaluated books and films in order to find out everything about gangsters and their era," Vavra says. "It was an enormous task to make the game come alive, and it took three years."

The story line takes place in a big city with hundreds of people and realistic streets and railway traffic. The game includes some 60 cars that are closely based on the original models, for example.

Even the programming, measured in terms of lines of code, can be a mammoth undertaking. Brian Reynolds, a developer on Microsoft's upcoming strategy game "rise of nations", estimates that the software will encompass roughly 850,000 lines of code. That kind of development for PC and console games can only be handled in teams. "Fifty people took part in the development of 'Anno 1503'," notes Juergen Reusswig from Sunflowers. "The development costs amounted to about three million dollars."

Yet historically accurate games aren't the only ones that can tax resources. Science fiction games such as Microsoft's upcoming space adventure "freelancer" occupied a team of three or four dozen people for four years, says head developer Joerg Neumann. Beyond the conceptual and programming efforts, such games require above all intensely fine graphics work.

The game elements often must be designed in two and sometimes three dimensions. Figures and props can only seem real when textured with some surface such as skin, fabric, wood, stones, or metal.

Another key part of the gaming fun is animation. Figures have to move around their artificial world believably. Sometimes this means that real-life actors need to be used, with their movements filmed and transferred onto the artificial figures using so-called motion capture technology.

But the best games also include built-in physical laws that lend the artificially created objects a sense of behavioral reality.

"When things hit each other, they then fly apart, the car bodies get bent, windows burst, tires roll away," is how Daniel Vavra describes physical effects built into "Mafia".

The different threads of game development run together in the hands of level designers, who create things like the background geography and landscapes, and who breathe life into the game world through its various finished parts. It is these special places and events that most often catch the eye and mind of players.

The role of music and sound also play big roles in computer games. As in films, the acoustical backdrop creates both atmosphere and tension. When characters in the fictional world talk to the player, the texts and dialogs need to have been fabricated in advance.

The final stop on the production chain is with the professional testers. They check the game for errors before the first paying customers get a look. The things that they catch or miss often determine whether a game will become a top-seller or a dud.