Inventing new game styles

Greg Costikyan has linked to this very interesting powerpoint, tip of the iceberg really that traces the lineage of how game styles dating back to early board games were conceived and evolutions of different gamestyles up to the current day and the impact that some have had.

http://www.costik.com/presentations/Imagining%20New%20Game%20Styles.ppt

I saved this as reference since although I have gone through the same exact thought process myself, this one nails it really concisely and I think I will be looking at it many times over the years whenever I run into "game designer's block"