I used the example of C2 own but when I export to android with Cocoon JS is so
Develop games in your browser. Powerful, performant & highly capable.
You have to use the correct dimensions or ratio. Also are you using the browser object to
"On any touch" > Request Fullscreen.
Are your publishing settings set to fullscreen or letterbox?
It takes some time to get the hang of getting the correct size and settings to fit and depends on your device.
Review the manual.