I can't play Trial of the kraken priestess (it's not a bug about the ACTUAL lol game)

I use a portable mac (os x, I think), I tried to play trial of the kraken priestess, but it's not working.. In the first level, I move the mouse through the shape (like it says), but I always fail.. i tried juts moving the mouse or moving WHILE clicking.

Am I playing wrong? Or it doesn't work on my computer?