you should insist on being paid. You agreed upon that in the beginning and with that you have made a contract. Send him an invoice. You get that behaviour a lot from people who want you to work for them. Well they still have to pay.
I totally understand your anger though. -_- Keep up your amazing work and don't let it drag you down ^^

I l ove it *O*
I'm still learning myself.
But judging from what you made here you're on a good way <3
Maybe the characters could be a bit darker since they are a bit hard to see...but that max. 22 colors regulation is probably the reason they aren't XD
Long Story short! I love it! I wish you the best of luck for this challenge.

I probably should ^^ I'm still learning.
Thanks for the comment <3