Simple but brilliant! I was trying to get used to triangles ...until I discovered the highlighting, then things got a lot easier. (yup, cos I didn't read the description. :p ) The fact that triangles are vertically asymmetrical brings a nice twist + what simon281084 says below about luck is a HUGE+!!
But: If I highlight many triangles side by side, the contrast weakens. - I had to constantly go click elsewhere to keep the contrast up.
A detail: the numbers don't all seem the same font weight/size? Somehow 4s seem to specially stand out... Or are my eyes playing tricks?