Draw lines to stop the fireballs from escaping the screen while the time counts down.
The lines you draw have limited life span and limited quantity so a clever style of drawing is needed to ensure that you do not run out of lines and that the lines you draw stay on the screen and do not disappear before the fireball rebounds.
You have to think a bit as you start progressing past the first couple of levels, bring your brain along.
Mix this fireball and drawing stuff with 51 levels and a funky back story to provide you with the motivation you need. Persevere and beat all the levels to see the happy ending.
There are also items to use and a whole bunch of other stuff like dragons and other flying junk to avoid all explained in the How To Play section in the game if you get all confused and do not know what to do, but really all you need to do is Keep In Play!