class {
    constructor() {
        this.state = { count:0 };
    }
    increment() {
        this.state.count++;
    }
}

style {
    .count {
        color:#09c;
        font-size:3em;
    }
    .example-button {
        font-size:1em;
        padding:0.5em;
    }
}

<div.count>
    ${state.count}
</div>
<button.example-button on-click('increment')>
    Click me!
</button>