hey people, hows everyone doing?

I need to do a project for class where I need to write my own encryption/decryption algorithm. Now it doesnt have to be uncrackable by the NSA or something like that, just something that works. It can by done in C, perl, python, java or anything else. My question is how do I begin. Do I first convert everything (plaintext, and key) to binary and run a bunch of methodical binary Exclusive Or's, bit shifts... on them. If so, does perl or python provide functions for EOring?
I just need some help getting started
Thanks in advance

pEaCe