Fun concept!
As the blocker is rotating around i found myself frustated and often using the wrong arrow-keys. Maybe using letters and then letting them sit on the blocker would help this? It was really hard to determine when the balls would rush towards the flag, but i guess that's the point haha. i'd love some sound effects on this one. Also, did the colors of the balls have any meaning to it?
Anyway, i had fun! lovely little game!