The "how many squares can you see" puzzle pops up on social networks from time to time. Some have taken to YouTube to explain it, that's a sizable datafile for conveying a moderately small amount of information, so I thought I'd put together an SVG+CSS version (no, there's no JavaScript) to provide a dynamic display of the 40 squares that can be found. Without compression or optimisation it's still less than 6K. See if you can find them all 40 squares first, then hover over each number to see the associated square to check your "work".