state-example.js

const HelpText = (props) => 
  <div {...props} style={css`
    font-family: Helvetica;
    padding: 10px;
    background-color: white;
    border: 1px inset #ccc;
  `} />;

const state = observable({ value: 0 });

autorun(() => 
   <HelpText>
    Current state value is {state.value}
   </HelpText>
);
        
<button onClick={() => state.value ++}>
  Increase state value
</button>;
                
<button onClick={() => state.value = 0}>
  Reset state value
</button>