Calculation sizing reference resource?

I’m in Studio, working with an advance grid in a section that I want to have end up as perfectly square cells, yet still be responsive over breakpoints (three cells wide on Desktop and Tablet, one cell wide on Phone)

I’m using 1fr for my per-column width setting, is there a way to use the Calculation sizing in the cell height to match the fluid size of the cell width?

so “row height = column width”

If that’s not the best way, then I’d be grateful for any suggestions for a better approach. I can’t use a Repeater, because there is no repetition of cell content. I have a container in each cell at the moment, inside which will be that cell’s unique design, but how to constrain to 1:1 is eluding me. Am I just being thick?

Many thanks in advance.