How to make it so that when you click on any category, a column with subcategories immediately starts to appear under it?

Question

css

On a small screen (mobile version), all categories are located in one column one after another and after them there are subcategories. It is necessary to make sure that when you click on any category, a column with subcategories will immediately appear below it, after which a list of categories will continue.
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Answer 1

Hide a div and show it on click. You can use bootstrap, there is a good panel for mobile devices.