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CSS Tips

Inline syntax

For simple use cases, the css property can be written as a HTML inline styles (without any CSS selector). CSS rules will apply to the widget element.

opacity: 0.5; /* make the widget's transparent */
font-size: 120%; /* increase font-size */

Selector syntax

CSS selectors can be used to apply styles to specific elements:

:host {
    /* style for the widget element
       & { } also works (deprecated)

.label {
    /* style for the .label elements */

> .label {
    /* style for the direct child .label element */

Mixing Inline and Selector syntaxes doesn't work, once you use selectors, you have to use the :host selector to target the widget element.

Layering: z-index

Z-Axis ordering can be set using the z-index rule. Absolutely positionned widgets (when top or left is different from auto) have z-index:10; by default.

Layering: pointer-events

To make a widget ignore interactions (ie to be able to click through it), add pointer-events:none;.

This is always ignored when the editor is enabled.

Responsive sizing

In most cases, using percentages in height and width will do. CSS calc() function can help in some cases:

:host {

    width: calc(100% - 100rem);


Media queries can also be used:

@media screen and (min-width: 768px) {

    :host {

        /* style the widget if the screen is bigger than 768px */



Size units

  • use rem instead of px (px values will not scale when zooming)
  • use % for font-size

CSS Variables

CSS Variables declared in the default theme can be overriden. Some widgets also use specific CSS variables (mostly to define colors) documented on their respective pages.

Other tips

Use the inspector

Hit F12 to open the developers tools panel. The html/css inspector helps retreiving the class names needed to style specific parts of the widgets.

Panel's background-color

This works for panel, strip and tabs:

> .panel {
    background-color: red;