ICT: What software is suitable for developing the multi-level game in the multimedia unit?

We are using PowerPoint or Flash depending on the ability of the pupils.  The majority of pupils are using PowerPoint.  I have had confirmation from a visiting moderator and Ann that these can be used.

we are not doing the game but we are doing tell me a story which I think would be similar requirements.  We are using powerpoint for basic animation embedded into Dreamweaver web pages for the majority of the story with flash for the final animated endings.