Introduction

Until now, little attention has been paid to the development of computer games that can be potentially played by all gamers, independently of their individual characteristics, requirements, preferences and abilities. In particular, there are no computer games that can be concurrently played among able and disabled people, either remotely or sharing the same computer, with the minor exception of a few games that can be played both by visually impaired and sighted players, like All inPlay card games and the 3D shooter Terraformers.

From a technical point of view, two main approaches have been adopted to address the issue of computer game accessibility:

• Inaccessible games become operationally accessible through the use of third-party assistive technologies, such as screen readers, mouse emulators, or special input devices. In practice there are serious barriers and bottlenecks inherent in the absence of compatibility efforts during the development of computer games and assistive technology systems. However, even when some sort of compatibility is achieved, this is typically the result of either customized low-level adaptations (hacking) or pure coincidence, rather than the outcome of appropriate design considerations.
• Accessible games are developed from scratch, however, targeted merely to people with a particular disability, such as audio-based games for blind people, and single-switch games for people with severe motor impairments on the upper limbs.

Following the first approach we typically accomplish a very limited form of accessibility, as well as poor interaction quality and usability. Through the second approach, being the most promising, we have to cope with two key drawbacks: (a) there is a significant tradeoff between the cost of developing high quality accessible games and the expected return on investment, assuming the target user group reflects a limited market population; and (b) there is an apparent hazard due to the potential segregation between able and disabled gamers, essentially leading to social exclusion.

In order to overcome the limitations of existing approaches towards game accessibility, the Human–Computer Interaction Laboratory of ICS-FORTH has introduced the concept of Universally Accessible Games, - UA-Games (Grammenos, Savidis, Stephanidis, 2005) - as an effective technical approach to achieve game accessibility coupled with high interaction quality, also putting forward the objective of creating games that are concurrently accessible to people with diverse abilities.

UA-Games are interactive computer games that:

• Follow the principles of Design for All, being proactively designed to optimally fit and dynamically adapt to different individual gamer characteristics without the need of further adjustments via additional developments.
• Can be concurrently played among people with different abilities, ideally also while sharing the same computer.
• May be played on various hardware and software platforms, and within alternative environments of use, utilizing the currently available devices, while appropriately interoperating with assistive technology add-ons.

UA-Games support the right of all people for equal opportunities in social interaction motivated by playing, putting forward inclusive entertainment as a key quality of an inclusive Information Society.

At present, in the context of the UA-Games research activity of the HCI Lab of ICS–FORTH, two games have been developed:

• UA–Chess: a universally accessible web–based chess.
• Access Invaders: a universally accessible multiplayer / multiplatform version of Space Invaders.