redefining @theme in @media

[adjkwdjax]

I attempted to implement responsive @theme changes in Tailwind CSS v4 using @media queries, but discovered that @theme directives don't support dynamic overrides within media queries. Instead, I used standard CSS custom properties defined in :root with proper media query ranges, then referenced those variables inside the @theme block (e.g., --spacing-card-width: var(--spacing-card-width);). This approach leverages Tailwind's theme system while maintaining full responsive control through native CSS cascade rules.

`@import "tailwindcss";

:root {
font-family: "IBM Plex Sans", sans-serif;

color-scheme: light dark;
color: rgba(255, 255, 255, 0.87);
background-color: #242424;

font-synthesis: none;
text-rendering: optimizeLegibility;
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale;

}

@theme {
/* custom breakpoints */
--breakpoint-1280w: 80rem;
--breakpoint-1440w: 90rem;
--breakpoint-1920w: 120rem;
--breakpoint-2560w: 160rem;
--breakpoint-3840w: 240rem;

--spacing-card-width: var(--spacing-card-width);
--spacing-card-height: var(--spacing-card-height);
/* other var's */

}

/* 1280w < res < 1440w /
@media (width >= 80rem) and (width < 90rem) {
:root {
/ video-card /
/ sizes */
--spacing-card-width: clamp(15rem,18.5vw + 1rem,30rem);
--spacing-card-height: clamp(15rem,25vw + 1rem,30rem);

        /* typography */
        --text-card-header: clamp(0.5rem,1.25vw + 0.5rem,2rem);
        --text-card-author: clamp(0.2rem,1.25vw + 0.2rem,1.2rem);
        --margin-card-left: clamp(1rem, 1vw, 1.5rem);

        /* margins and paddings */
        --margin-card-left: 0.8rem;
        --margin-card-right: 0.8rem;
        --margin-card-top: clamp(16.5rem,20vw + 0.5rem,18.5rem);
    /* video-card  */
    /* todo */
}

}

/* 1440w < res < 1920w /
@media (width >= 90rem) and (width < 120rem) {
:root {
/ video-card /
/ sizes */
--spacing-card-width: clamp(15rem,18.5vw + 1rem,30rem);
--spacing-card-height: clamp(15rem,25vw + 1rem,30rem);

        /* typography */
        --text-card-header: clamp(0.5rem,1.25vw + 0.5rem,2rem);
        --text-card-author: clamp(0.2rem,1.25vw + 0.2rem,1.2rem);
        --margin-card-left: clamp(1rem, 1vw, 1.5rem);

        /* margins and paddings */
        --margin-card-left: 0.8rem;
        --margin-card-right: 0.8rem;
        --margin-card-top: clamp(16.5rem,20vw + 0.5rem,18.5rem);
    /* video-card  */
    /* todo */
}

}`

[anntnzrb]

Your workaround is the correct approach - @theme blocks must be top-level (not in @media) because they instruct Tailwind to generate utilities at build time. Define responsive CSS variables in :root with media queries, then reference them in @theme:

@theme {
  --spacing-card-width: var(--spacing-card-width);
}

@media (width >= 80rem) {
  :root {
    --spacing-card-width: clamp(15rem, 18.5vw + 1rem, 30rem);
  }
}

This works because @theme registers the variable with Tailwind at build time, while the actual values are overridden at runtime via CSS cascade.