portfolio/pages/_app.tsx

import { createGlobalStyle, ThemeProvider } from 'styled-components'

const GlobalStyle = createGlobalStyle`
    body {
        margin: 0;
        padding: 0;
        font-family: 'Open Sans';
    }
`

const theme = {
    colors: {
        primary: '#f2f0ed',
        background: '#080a0b'
    },
}

export default function App({ Component, pageProps }) {
    return (
        <>
            <GlobalStyle />
            <ThemeProvider theme={theme}>
                <Component {...pageProps} />
            </ThemeProvider>
        </>
    )
}