Thank you for your feedback! The start screen in the WebGL version is a bit messed up, the control guide is hidden by buttons, if you download the Windows version they are visible :P
But you throw a light by clicking/holding Left Ctrl or Left Mouse button, the longer you hold the key down the more force is added to the throw. I hard a hard time figuring out what would be the most intuative key to use for that function :)
Again thank you for your feedback!