If you can't see the continue button on the "Make your monster" screen, this sometimes happens if the browser doesn't have enough display space to show the entire game.
Try ‘zooming out’ on your browser, or hiding some of the toolbars at the top of your browser window.
To make the game fit on your screen, you can follow these steps for Google Chrome:
Press the three dot icon at the top right of your browser
Navigating to the Zoom section, press the minus button