just to nit-pick:
Quote: "I have just started to program for the first time and it just happens to be for my Advanced Higher Computing project."
you've started something like Advanced higher computing, When I did computing at A-level programming was a compulsory module. Now, I don't know about your education history, but to jump straight in at advanced higher computing, with no prior programming experience seems silly. Plus, the words Advanced, and Higher in the title name suggest you're going to be expected to use a lower-level language than basic...
The place to start is pong, nice and simple ... then 3D pong, which even shows about collision (between ball and bat). At which point you might be better experienced to tackle a shooter game.
and, as for AI, well, that's difficult, particularly if you want it to be lifelike...