import React, { useState } from 'react'; import ReactDOM from 'react-dom'; import styled from 'styled-components'; import CssBaseline from '@material-ui/core/CssBaseline' import Header from './components/Header/Header'; import Timer from './components/Timer/Timer'; const App = () => { const [page, setPage] = useState('app'); return ( <Root> <CssBaseline/> <Header setPage={setPage} /> <h1> This is the {page} page! </h1> <p> This text is rendered outside of <code>Header</code> component, but interacting with <code>Header</code> can influence content of this page! </p> <Timer /> </Root> ); }; const Root = styled.div` background: cornsilk; padding-bottom: 25px; `; ReactDOM.render(<App />, document.getElementById('root'));