How to invoke the android keyboard using JavaScript without a text field?

So I copied one of my small JavaScript games to my android phone and ran it in the browser. The game worked fine, except one fatal flaw: The game requires keyboard input, and it doesn't have a text field.

The game requires the user to type in certain letters, but they don't type it into a text field. I use a keydown event listener to get each key and process it accordingly.

So how do I invoke the android keyboard without having an actual text field?