why only PowerPoint 2007+ can run redasteroid?

When you download the game, you may notice that the file type is PPSM .. This is one of the types of PPTX files (presentation file).  Before the 2007 version of PowerPoint, the file type was PPT ,this type was first used actually in PowerPoint 95! and it was so old that the functions that Microsoft wanted to implement not worked.. and because of this PPTX was invented.. and the first version that supported this type was PowerPoint 2007. Now it’s clear why you can play Redasteroid only with PowerPoint 2007.

Microsoft- "The main difference between PPT and PPTX files is the fact that the XML version are considered “open source”.  This means that it is much easier for other types of presentation programs to open files saved in the PPTX format."