Responsive means that your design looks good on a variety of screen sizes and devices - all the way from wide screens found on desktops and laptops to small screens found on tablets and phones.
Responsive design is achieved by setting different styles for elements depending on the width of the browser viewport - e.g. stacking columns vertically or using a smaller font size below a certain width.
Previewing At Different Widths
To preview your design at various screen widths, click any element, then click the device icon at the left to open the device dropdown.
Then choose a width from the device dropdown to preview your design at that width.
By default, Oxygen displays your responsive preview at one pixel wider than the next smallest width from the width you have chosen.
To adjust the preview width, click the responsive ruler at the bottom of the screen, then drag it left or right.
Creating Responsive Styles
In Oxygen, most properties can have different values for each browser viewport width.
To customize the value of a property for a particular width, select the screen width you wish to create styles for from the device dropdown.
All edits made to the property at this width will only take effect at this width and below.
Hiding Or Showing Elements Based On Screen Width
To hide an element below a certain screen width, choose the screen width you wish to hide the element below from the device dropdown. From Advanced > Layout, set the display property to none.
To show an element below a certain screen width, choose All devices from the device dropdown and set the display property to none. Then choose the screen width below which you want the item to be visible, and set the display property back to block, flex, etc. as appropriate.
Responsive Columns
Oxygen's Columns element is responsive by default, and has special responsive settings to customize and control the layout and order of your columns on narrower screens.
Stack Vertically Below – Below the chosen screen width, columns will stack vertically.
Reverse Column Order Below – Below the chosen screen width, the columns will be displayed in reverse order. This is useful for achieving a consistent layout when columns are stacked vertically for alternating column layouts.
50% Width Below – This is useful for multiple-column layouts with four or more columns, when the columns should be 50% width on medium width screens and stack vertically on narrow screens.
Responsive Menus
Oxygen's Menu element is responsive by default and will collapse into a toggle at 992px.
This can be customized at Primary > Mobile Responsive for the menu element.
Other settings are also available to adjust the menu styles, adjust the icon style, and to show or hide dropdown links in the responsive menu.
Deleting Responsive Styles
To delete the responsive styles created for a particular width, click the device icon to open the device dropdown. Then click the red X next to the screen width to delete all styles set for that width.
Further Reading
https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Using_media_queries