Header.jsx

import React from 'react';
import { css } from 'emotion'; 
import TLogo from './TLogo';

const black = '#000';
const logoClass = css`
  height: 24px;
  width: 24px;

  @media (min-width: 800px) {
    height: 48px;
    width: 48px;
  }
`;

export default function Header() {
  return (
    <header>
      <TLogo fill={black} className={logoClass} />
    </header>
  );
}