OOoo, poor you, sorry I'm laughing because I can remember my own little sod DD doing very similar at that age & beyond 
if its any reasurrance, it seems it can be the bright ones that quickly learn to take the power out of any punishments, so I quickly learned to think on my feet & through the "naughty step" rule book out of the window
I had to keep changing the goal posts, for a while rewards over punishments would work better,
for example I decorated 10 pennies & she had to get through X amount of time without misbehaving & she would then be given a "flower coin" if she still misbehaved after warnings, she had 1 taken off her instead....she collected 10, & she got to choose a treat, anything from a trip somewhere she liked, to & trip to the Pound shop, with money to spend on anything she chose
this worked brilliantly for a while, until she decided not to "spend" them any more, that way she didn't have to earn them
.....so reverted back to a punishment routine for a while...removing toys...until 1 day she brought me a basket of her favourites & said, there I don't want them]
...& on & on....
she kept me on my toes alright, but all good fun, & she is now 8, very bright & generally very well behaved :)
so from my experience, your going to have to keep changing how you deal with it, but be secretly proud you've probaly got a brian box on your hands 