What are the best practices for having a product card laid out horizontally or vertically? Can a product card be laid out both ways? If so, my concern is breaking user's mental map of how they're reading the product cards.
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I would say it primarily depends on screen size and orientation.
These factors affect the amount of space available to convey information and ideally you can convey a single piece of information in one line. Imagine you have a long product name; if you are using a horizontal layout on a large screen, the name will likely fit in a single line. However, if you are using a vertical layout, the information may be split into multiple lines. This is bad because your pieces of information information are no longer split up by verticality.
The best approach would be to use one layout or the other for consistency's sake. Consider your platform and the amount of information you will be conveying and make a choice based on that.
