export declare function px(value: number | string): string;
/**
 * Convert px values to rem units.
 * A special opinionated measurement inspired by Stylus "rex".
 * We assume that 1rem == 16px, so 1rex == 0.0625rem.
 * The advantage is that sizes nicely scale to different default font sizes.
 *
 * @param value - Number (treated as px) or string with unit
 * @returns Value converted to rem, or original string if it already has a unit
 *
 * @example
 * rex(16) // '1rem'
 * rex(8) // '0.5rem'
 * rex('24px') // '1.5rem'
 * rex('2rem') // '2rem' (unchanged)
 * rex(0) // '0'
 */
export declare function rex(value: number | string): string;