This is another 3D Chess variant.
This game has to main variants.
The most well known is Cheops Chess which is mentioned in the Dune series.
The other is simply called Pyramid Chess.
Both have levels that decrease in size as you go from bottom to top, hence the reference to a pyramid.
I'm not sure which would be better, so start with 9x9, 8x8 or 7x7.
I lean towards the odd numbered base because the top level ends up being one cube rather than four.