content: import React from 'react';
  import ReactDOM from 'react-dom';
  import copal from 'copal';
  
  export const TodoApp = copal(
      (state, actions) =>
          <div>
              <button onClick={actions.decrement}>-</button>
              <div>{state.value}</div>
              <button onClick={actions.increment}>+</button>
          </div>
      ,  
      {
          initialize: a => a.map( s => ({value: 0})),
          increment: a => a.map( s => ({value: s.value + 1})),
          decrement: a => a.map( s => ({value: s.value - 1})),
      }
  )
  
  ReactDOM.render(TodoApp, document.getElementById('root'));