I'm very happy to say that scrolling up now works too! After all, with a bit struggling, it was so easy people will bump their heads when they hear what I tried Anyway, here's a screenshot so far:
While I had some free time today, I implemented the boundaries checking for vertical scrolling. You can't go up if you're at the first line, and not going down, if at the last line. It still doesn't work 100%, so I need to fix the bugs somehow. Now screenshot available