The player adapts to give you the fullest screen possible, although there is no full-screen button, and you can maximise your browser window on the device you are watching on.
To maximise your browser window and remove the tabs:
On a mac: click the green button in your browser window or go to 'View' - 'Enter Full Screen' (ensure that your toolbar isn't set to always show)
On a PC: press 'F11'
You'll always see the thumbnails at the bottom of the screen, as that is part of our unique player and viewing experience!