Grapefruit bars

I love lemon bars. There is something about that tangy filling with the buttery crust which makes it a perfect cokie to me. I have seen recipes for lime bars as well. I have not tried to make them, but it did get me thinking.....what other citrus could be used in this type of recipe? Grapefruit came to mind.... I was thinking Rubt Red grapefruit would be ideal. I think my next endeavor will be to make a basic recipe for a citrus bar.... Grapefruit, clementine, cuties, lime, and of course good ol' lemon......I bet we could even go further.....Maybe even persimmon, kiwi, pineapple...... Boy my brain is getting geared up.