In order to improve the appearance of the buttons let us use the css.
In html file we should add after the <html> tag the following code:
<style> .button { background-color: #4CAF50; border: none; color: white; width:100%; padding: 15px 32px; text-align: center; font-size: 20px; margin: 4px 2px; cursor: pointer; }</style>At the definition of the buttons the class .button should be added (class="button"):
<button id="buttonOn1" class="button" onClick="on1()">On 1</button><button id="buttonOff1" class="button" onClick="off1()">Off 1</button><button id="buttonOn2" class="button" onClick="on2()">On 2</button><button id="buttonOff2" class="button" onClick="off2()">Off 2</button>The new buttons should look like: