Category Hierachy – Only Display Parent

Hello all

I’m currently trying to configure my new wordpress site, which will have a lot of categories.

http://www.tew-dynasties.co.uk/

To avoid numerous categories from clogging up the side menu, I only wish to display the parent category, until it is clicked on by a browser.

E.g
A current game, which will have categories such as show type 1, show type 2, show type 3 etc.
If there were numerous games being blogged about, the menu would be never ending. Instead I only want the parent category to be there, once it’s clicked i’d like it to expand/collapse to show the sub categories.

I’ve had a look at some examples here, but none have worked correctly.

Could you please help?