Human-computer interaction (HCI), especially in the games domain, targets to mimic as much as possible the natural human-to-human interaction, which is multimodal, involving speech, vision, haptic, etc. Furthermore, the domain of serious games, aiming to value-added games, makes use of additional inputs, such as biosensors, motion tracking equipment, etc. In this context, game development has become complex, expensive and burdened with a long development cycle. This creates barriers to independent game developers and inhibits the introduction of innovative games, or new game genres. In this paper the PlayMancer platform is introduced, a work in progress aiming to overcome such barriers by augmenting existing 3D game engines with innovative modes of interaction. Playmancer integrates open source existing systems, such as a game engine and a spoken dialog management system, extended by newly implemented components, supporting innovative interaction modalities, such as emotion recognition from audio data, motion tracking, etc, and advanced configuration tools.