code block font-size not changeable?

I am finding no way to change the font-size for a code block in the WordPress block editor using the Blocksy theme. The block typography in the block editor seems mostly to be non-functional for a code block. In particular, the font-size makes no visible difference. I even tried custom CSS, and it had no effect (I could set, for example, the text color via custom CSS, but font-size made no difference, even with !important).

My goal here was originally to have two <code> blocks side-by-side, so the reader can compare the two, line-by-line. I can do that on the desktop view, but, for tablet and mobile views, the text in the <code> blocks, when too long for the line, gets wrapped to the next line. I would like to reduce the font size to compensate for this, but found that I have no control over the font-size for the <code> block.

Can someone help me figure this out?

Thanks!

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