Wordwall is a popular tool for making and delivering attractive, interactive activities. These activities can be embedded on Moodle using the Poodll Wordwall widget. If they are embedded in this way then they will resize nicely to fit the screen regardless of the device that the student is using.

First you need to get the share URL for the Wordwall resource. Click the "Share" button on the lower right of the activity and then click "copy" beide the activity share URL. 

Then on your Moodle / Poodll site choose the Wordwall widget from the Poodll widgets dialog.

Paste in the wordwall URL that you copied earlier:

Now when the page is displayed the Wordwall activity will be embedded and size itself nicely.