Most of the tasks appeared to consist of finding enemy agents (identified by their coloured clearance level, e.g. purple) and shooting them.
Unfortunately, despite the name (CPC = Colour Personal Computer), the one I had bought second-hand had a monochrome (green) monitor—so I could never identify any purple or red or other agents. (Each colour mapped to a distinct shade of green, so the game was not completely impossible, only practically impossible.)
I think I ended up giving the game away to a friend, even though I had paid a fair bit of money for it. (On a visit to England, so I couldn't just bring the game back to the shop, either.)