Responsive editing & breakpoints

The device icons in the top bar switch the active breakpoint. Whatever breakpoint is active when you change a style — padding, font size, width, anything — is the only one affected. Switch to Tablet and shrink a heading's font size, and Desktop keeps its original value untouched.

Unset values fall through the cascade: a property you never touch on Tablet or Mobile simply inherits whatever Desktop set. This means you only ever need to override the properties that actually need to change at a smaller size.