I am on the hunt for a layout that caught my eye some time ago, but unfortunately I forgot to save it. It featured 3 main columns that cleverly transformed into 2 when resized, causing the 3rd column to shift to the row below. It wasn't your typical layout adjustment with overflow.
As it resized, all 3 columns maintained the same width until they reached a certain threshold, at which point each one occupied 33% of the width while increasing in height. The only noticeable change was in the text size. Then, during further resizing, one column would drop down to the next row, allowing the 2 remaining columns to expand and fill up the entire width (50% each) while the dropped column took up the full 100% width of its new row. Despite extensive Googling, I couldn't pinpoint the exact terms due to not being a native English speaker. I distinctly remember that the layout worked flawlessly in the demo using only CSS and HTML.
EDIT: The container holding the 3 columns maintained the same width throughout the resizing process.