button.js

import React, {Component} from 'react';
import ReactDOM from 'react-dom';

import Style from 'style-it';

class Button extends Component {
  render() {
    return Style.it(`
      .container {
        text-align: center;
      }
      .button {
        background-color: #ff0000;
        width: 320px;
        padding: 20px;
        border-radius: 5px;
        border: none;
        outline: none;
      }
      .button:hover {
        color: #fff;
      }
      .button:active {
        position: relative;
        top: 2px;
      }
      @media (max-width: 480px) {
        .button {
          width: 160px;
        }
      }
    `,
      <div className="container">
        <button className="button">Click me!</button>
      </div>
    );
  }
}

ReactDOM.render(<Button />, document.getElementById('content'));