# Theming
This page includes all documentation regarding WooCommerce Blocks and themes.
## General concepts
### Global styles
WooCommerce blocks rely on [global styles](https://developer.wordpress.org/themes/global-settings-and-styles/styles/) for their styling. Global styles can be defined by themes via `theme.json` or by users via Appearance > Editor > Styles and offer several advantages over plain CSS:
* Better performance, as only the required CSS is printed into the page, reducing the bundle size to render a page.
* Can be easily customized by users via the UI.
* Gracefully handle conflicts between plugins and themes.
* Are not affected by markup or class name updates into individual blocks or components.
* Don't depend on a specific nesting order of blocks: users can freely move blocks around without styles breaking.
#### Example
For example, let's imagine you are building a theme and would like to customize the Product Price block styles, you can do so by adding these properties in your `theme.json`:
```JSON
"styles": {
"blocks": {
"woocommerce/product-price": {
"color": {
"background": "#00cc00",
"text": "#fff"
},
"typography": {
"fontStyle": "italic",
"fontWeight": "700"
}
}
...
}
...
}
```
Before | After
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You can find more [documentation on global styles](https://developer.wordpress.org/themes/global-settings-and-styles/styles/) in developer.wordpress.org. You can also find the [list of WooCommerce blocks and their names in the docs](../../block-references/block-references.md).
### Block and component class names
**Important: we strongly discourage writing CSS code based on existing block class names and prioritize using global styles when possible. We especially discourage writing CSS selectors that rely on a specific block being a descendant of another one, as users can move blocks around freely, so they are prone to breaking. Similar to WordPress itself, we consider the HTML structure within components, blocks, and block templates to be “private”, and subject to further change in the future, so using CSS to target the internals of a block or a block template is _not recommended or supported_.**
WooCommerce Blocks follows BEM for class names, as [stated in our coding guidelines](../../contributors/coding-guidelines.md). All classes start with one of these two prefixes:
* `.wc-block-`: class names specific to a single block.
* `.wc-block-components-`: class names specific to a component. The component might be reused by different blocks.
The combination of block class names and component class names allows themes to style each component either globally or only in specific blocks. As an example, you could style all prices to be italics with:
```css
/* This will apply to all block prices */
.wc-block-components-formatted-money-amount {
font-style: italic;
}
```
But if you only wanted to make it italic in the Checkout block, that could be done adding the block selector:
```css
/* This will apply to prices in the checkout block */
.wc-block-checkout .wc-block-components-formatted-money-amount {
font-style: italic;
}
```
**Note:** for backwards compatibility, some components might have class names with both prefixes (ie: `wc-block-sort-select` and `wc-block-components-sort-select`). In those cases, the class name with `.wc-block-` prefix is deprecated and shouldn't be used in new code. It will be removed in future versions. If an element has both classes always style the one with `.wc-block-components-` prefix.
### Container query class names
Some of our components have responsive classes depending on the container width. The reason to use these classes instead of CSS media queries is to adapt to the container where the block is added (CSS media queries only allow reacting to viewport sizes).
Those classes are:
Container width | Class name
----------------|------------
\>700px | `is-large`
521px-700px | `is-medium`
401px-520px | `is-small`
<=400px | `is-mobile`
As an example, if we wanted to do the Checkout font size 10% larger when the container has a width of 521px or wider, we could do so with this code:
```css
.wc-block-checkout.is-medium,
.wc-block-checkout.is-large {
font-size: 1.1em;
}
```
### WC Blocks _vs._ theme style conflicts for semantic elements
WooCommerce Blocks uses HTML elements according to their semantic meaning, not their default layout. That means that some times blocks might use an anchor link (``) but display it as a button. Or the other way around, a `