// Bad
<div className="flex flex-col gap-4">
<div className="flex flex-row gap-4">

// Good
<div className="v-stack gap-4">
<div className="h-stack gap-4">

// Bad
<div>
  <Item className="mb-4" />
  <Item className="mb-4" />
</div>

// Good
<div className="flex flex-col gap-4">
  <Item />
  <Item />
</div>

// Mobile: vertical, Desktop: horizontal
<div className="v-stack lg:h-stack gap-4">
  <main className="grow">...</main>
  <aside className="shrink-0 lg:w-80">...</aside>
</div>

// Mobile: horizontal, Desktop: vertical
<div className="h-stack md:v-stack">

<button className="rounded-full bg-gray-900 px-4 py-2 text-white dark:bg-gray-100 dark:text-gray-900">
  Toggle
</button>

import { cn } from "~/lib/cn";

function Button({ className, variant }: Props) {
  return (
    <button
      className={cn(
        "base-classes",
        {
          "variant-primary": variant === "primary",
          "variant-secondary": variant === "secondary",
        },
        className, // external className always last
      )}
    />
  );
}

import type { ClassName, ClassNameRecord } from "~/lib/cn";

// Single element
type Props = {
  className?: ClassName;
};

// Multiple elements
type Props = {
  className?: ClassNameRecord<"root" | "label" | "input">;
};

// Usage
<Input className={{ root: "w-full", label: "font-bold" }} />;

<label className="ui-button" htmlFor="document-upload">
  Choose file
</label>

// Standard breakpoints (min-width)
<div className="px-4 md:px-8 lg:px-12">

// Show/hide with standard breakpoints
<div className="hidden md:block">Desktop only</div>
<div className="md:hidden">Mobile only</div>

// Responsive font size
<h1 className="text-2xl md:text-3xl lg:text-4xl">

// Responsive line height with text
<p className="text-sm leading-5 md:text-base md:leading-6">

<button className="h-10 w-10 pointer-coarse:h-12 pointer-coarse:w-12">
  <Icon />
</button>