sudo: apt: command not found while installing

[kriti.mysty]

so i was removing softwares using ubuntu software center.. games i don't play and cheese webcam booth because it was not working, i intended to re-install it. after my installation, half my icons (i have extensively personalized my desktop) changed to defaults. The themes page said 'theme will not be as it appears because default.kde is not installed'. i did not remove any such package. just games. and furthermore, i installed a kubuntu plasma desktop system which i read in a thread contains the file default.kde
but that hasn't helped and i still don't know what do to..
any help will be appreciated. thanks in advance.

[jerrrys]

you haven't knowingly removed any packages, but you have removed dependencies. something that the software center will not tell you, when doing removal, you should use "synaptic package manager", its in the software center. this package manager will tell you what dependencies you are about to remove.