sta HMOVE is exactly what I was missing, thanks.
That sounds pretty difficult.. I think I might leave paddle for a later project, since I wouldn't even have a way to play it with an actual paddle anyway.
I was calling it correctly but I was missing the HMOVE call, I got it to work now.
Sorry I didn't look much into it at first, I was already getting kinda overwhelmed by the guide I was trying to follow but yours is much clearer. I started rewriting my code using your timer source as a template and I got everything to work more or less right, but I'm still getting some oddities I'll work out later. That code is on my GitHub now, I hope it's okay to use your code as a starting point. I've credited you in the comments.
Thanks for the help so far, everybody!