Responsive behaviour

Every gallery responds to its own width, not the width of the browser window. A gallery in a narrow column behaves like a gallery on a phone, whatever the screen. Below the tablet width (1000px by default) columns drop and rows get shorter. Below the mobile width (640px by default) they drop again. Resize the browser to see the layouts reflow, or compare the same gallery at three widths.

Set to 3 columns, 2 at tablet width and 1 at mobile width. At 900px wide (under the 1000px tablet width) the grid drops to 2 columns, and at 500px wide (under the 640px mobile width) to 1. The sidebar demo at the bottom of the page shows the same thing from layout alone.

Rows get shorter as the gallery narrows (80 percent of the row height at tablet width, 60 percent at mobile width), and the rows are rebalanced for the new width.

A 600px wide container with the tablet width set to 500 and the mobile width set to 300 keeps its three columns. The default breakpoints would have collapsed it to one.

The same element in a main column and in a 300px sidebar, on one browser window. The main column is under the tablet width so it shows 2 columns. The sidebar is under the mobile width so it shows 1.