new mac league is a little white spec HELP ME !!!

so i got the macbook pro 13 retina display version 10.10.2 today. when i downloaded league it was fine but when i tried to open it all i got was a little white spec on my screen. I have read up on it and it says it doesn't support anything below 10.6 but mine is above so why is my new mac having the same problem? if anyone could help i would really appreciate it.