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Sass Customization

Sass customization is the build-time half of bestax's two-layer theming story. You set Bulma's Sass variables once at build time to bake in defaults (brand colors, fonts, radii); then bestax's Theme component lets you adjust any of them at runtime via CSS variables. The two layers are designed to work together — Sass defines what ships, Theme adjusts what renders.

Bulma's canonical reference

The authoritative documentation for customizing Bulma with Sass lives on the Bulma site:

This page focuses on wiring a Bulma Sass build into a bestax React project; refer to Bulma's docs for the variable reference and Sass semantics.

Do you actually need a custom Sass build?

If you came in through npm create bestax@latest, you already picked one of the prebuilt Bulma flavors shipped with this library (bestax-prefixed, bestax-no-helpers, bestax-no-dark-mode, etc. — see bulma-ui/src/scss/versions/). Those are modular Sass builds of Bulma. That, plus runtime overrides through Theme, covers most projects. Reach for a custom Sass build when you need design tokens (brand colors, typography, control sizes) baked into the CSS that ships to users.

Overview​

Sass variables feed the generated Bulma CSS — including the values of Bulma's CSS custom properties. Customize them at build time to set the defaults of your design system; then use the Theme component (or raw CSS variables) to override those defaults at runtime.

Dependencies​

To customize Bulma with Sass variables, you need:

npm install sass
npm install bulma

Build Configuration​

Vite​

Vite is the default toolchain for projects scaffolded by npm create bestax@latest, and handles Sass out of the box once sass is installed:

npm install sass

src/styles/bulma-custom.scss:

@use 'bulma/sass' with (
  $primary: #e91e63,
  $family-primary: '"Roboto", sans-serif',
  $radius-large: 12px,
  $control-height: 3rem
);

Import directly in your entry:

// src/main.tsx
import './styles/bulma-custom.scss';
import { Button, Container } from '@allxsmith/bestax-bulma';

function App() {
  return (
    <Container>
      <Button color="primary">Vite + Sass Button</Button>
    </Container>
  );
}

Next.js​

Next.js has built-in Sass support:

Install Sass:

npm install sass

Custom Sass file (styles/bulma-custom.scss):

@use 'bulma/sass' with (
  $primary: #0070f3,
  $family-primary: '"Inter", sans-serif',
  $navbar-height: 4rem,
  $footer-padding: 3rem 1.5rem
);

Import in _app.tsx:

// pages/_app.tsx
import '../styles/bulma-custom.scss';
import type { AppProps } from 'next/app';

export default function App({ Component, pageProps }: AppProps) {
  return <Component {...pageProps} />;
}

Use in pages:

// pages/index.tsx
import { Hero, Container, Title, Button } from '@allxsmith/bestax-bulma';

export default function Home() {
  return (
    <Hero size="medium">
      <Hero.Body>
        <Container>
          <Title>Next.js + Sass Customization</Title>
          <Button color="primary" size="large">
            Get Started
          </Button>
        </Container>
      </Hero.Body>
    </Hero>
  );
}

Webpack / Create React App​

Create React App is no longer actively developed — new projects should prefer Vite or Next.js. If you're maintaining an existing CRA app, you can compile a custom Sass file with a standalone sass CLI script and import the generated CSS:

{
  "scripts": {
    "build-bulma": "sass --load-path=node_modules src/styles/bulma-custom.scss src/styles/bulma-custom.css",
    "watch-bulma": "npm run build-bulma -- --watch"
  }
}
import './styles/bulma-custom.css';

Common Sass Variables​

The snippets below show the variables most projects customize. For the full catalog — initial, derived, and component-level — refer to Bulma's List of Sass variables.

Color Variables​

@use 'bulma/sass' with (
  // Primary colors
  $primary: #3273dc,
  $link: #3273dc,
  $info: #3298dc,
  $success: #48c774,
  $warning: #ffdd57,
  $danger: #f14668,

  // Neutral colors
  $white: #ffffff,
  $black: #0a0a0a,
  $light: #f5f5f5,
  $dark: #363636,

  // Grey shades
  $grey-darker: #121212,
  $grey-dark: #363636,
  $grey: #4a4a4a,
  $grey-light: #b5b5b5,
  $grey-lighter: #dbdbdb
);

Typography Variables​

@use 'bulma/sass' with (
  // Font families
  $family-sans-serif: '"Inter", "SF Pro Display", sans-serif',
  $family-monospace: '"Fira Code", "SF Mono", monospace',
  $family-primary: $family-sans-serif,
  $family-secondary: $family-sans-serif,
  $family-code: $family-monospace,

  // Font sizes
  $size-1: 3rem,
  $size-2: 2.5rem,
  $size-3: 2rem,
  $size-4: 1.5rem,
  $size-5: 1.25rem,
  $size-6: 1rem,
  $size-7: 0.875rem,

  // Font weights
  $weight-light: 300,
  $weight-normal: 400,
  $weight-medium: 500,
  $weight-semibold: 600,
  $weight-bold: 700
);

Layout Variables​

@use 'bulma/sass' with (
  // Spacing
  $block-spacing: 1.5rem,
  $column-gap: 0.75rem,

  // Border radius
  $radius-small: 2px,
  $radius: 4px,
  $radius-medium: 6px,
  $radius-large: 8px,
  $radius-rounded: 9999px,

  // Control elements
  $control-height: 2.5em,
  $control-line-height: 1.5,
  $control-padding-vertical: calc(0.5em - 1px),
  $control-padding-horizontal: calc(0.75em - 1px)
);

Component Variables​

@use 'bulma/sass' with (
  // Button
  $button-padding-vertical: 0.5rem,
  $button-padding-horizontal: 1rem,
  $button-border-radius: $radius,

  // Input
  $input-shadow: inset 0 0.0625em 0.125em rgba(10, 10, 10, 0.05),
  $input-hover-border-color: $grey-dark,
  $input-focus-border-color: $link,

  // Card
  $card-shadow: 0 0.5em 1em -0.125em rgba(10, 10, 10, 0.1),
  $card-radius: $radius-large,

  // Navbar
  $navbar-height: 3.25rem,
  $navbar-padding-vertical: 1rem,
  $navbar-padding-horizontal: 2rem
);

How Sass Feeds Bulma's CSS Variables​

In Bulma v1, the values you pass to @use 'bulma/sass' are compiled into the defaults of the CSS custom properties Bulma exposes — see Bulma's Concepts page for the end-to-end flow from Sass variable to generated CSS variable:

@use 'bulma/sass' with (
  $primary: #ff6b35,
  $family-primary: '"Helvetica Neue", sans-serif'
);
:root {
  --bulma-primary-h: 18deg;
  --bulma-primary-s: 100%;
  --bulma-primary-l: 60%;
  --bulma-family-primary: '"Helvetica Neue", sans-serif';
}

Those same CSS variables can be re-addressed at runtime through bestax's Theme component — so Sass sets the baseline, Theme overrides as needed.

Integration with React Components​

Build-time Theme​

// styles/corporate-theme.scss
@use 'bulma/sass' with (
  $primary: #1e3a8a,
  // Corporate blue
  $success: #059669,
  // Corporate green
  $family-primary: '"Open Sans", sans-serif',
  $radius: 2px,
  // Sharp corners
  $control-height: 3rem // Larger controls
);
// App.tsx
import './styles/corporate-theme.css';
import { Button, Card, Container, Title } from '@allxsmith/bestax-bulma';

function CorporateApp() {
  return (
    <Container>
      <Card>
        <Card.Content>
          <Title>Corporate Design System</Title>
          <Button color="primary">Corporate Button</Button>
          <Button color="success" ml="2">
            Action Button
          </Button>
        </Card.Content>
      </Card>
    </Container>
  );
}

Combining with CSS Variables​

You can use both approaches together - Sass for base configuration and CSS variables for runtime theming:

// Base theme with Sass
@use 'bulma/sass' with (
  $family-primary: '"Inter", sans-serif',
  $radius: 6px,
  $control-height: 2.75rem
);
// Runtime theming with CSS variables
import { Theme } from '@allxsmith/bestax-bulma';

function App() {
  return (
    <Theme primaryH="270" primaryS="100%" primaryL="50%" isRoot>
      <CorporateApp />
    </Theme>
  );
}

Best Practices​

1. Establish Design Tokens​

Define your design system values clearly:

// design-tokens.scss
$brand-blue: #1e40af;
$brand-green: #059669;
$brand-orange: #ea580c;

$font-primary: '"Inter", sans-serif';
$font-mono: '"JetBrains Mono", monospace';

$spacing-unit: 0.25rem;
$border-radius-base: 6px;

@use 'bulma/sass' with (
  $primary: $brand-blue,
  $success: $brand-green,
  $warning: $brand-orange,
  $family-primary: $font-primary,
  $family-code: $font-mono,
  $radius: $border-radius-base
);

2. Modular Sass Files​

Organize your customizations by feature:

// styles/main.scss
@use './variables' as vars;
@use './typography';
@use './components';

@use 'bulma/sass' with (
  $primary: vars.$brand-primary,
  $family-primary: vars.$font-family-base
);

3. Environment-specific Builds​

Create different themes for different environments:

// themes/development.scss
@use 'bulma/sass' with (
  $primary: #ef4444,
  // Red for development
  $warning: #f59e0b
);

// themes/production.scss
@use 'bulma/sass' with (
  $primary: #3b82f6,
  // Blue for production
  $warning: #f59e0b
);

Pairing Sass Defaults with Runtime Overrides​

A typical bestax project uses both layers together: Sass sets shipped defaults, Theme adjusts them per-context or per-user.

@use 'bulma/sass' with (
  $primary: #8b5cf6,
  $radius: 8px
);
<Theme
  primaryH="258"
  primaryS="90%"
  primaryL="64%"
  bulmaVars={{ '--bulma-radius': '12px' }}
>
  <App />
</Theme>

Further Reading​