Thanks for the comments, folks.
>about HD
The original raw video in my PC is coded with H.264, resolution of 1280*960 (it's huge lol) and it seems YouTube automatically converts it into 960*720 when uploaded.
>math
Yeah, that 'math' part is pretty complicated, that's my best effort to describe in simple expressions. It's pretty usual for me to take more than an hour to write a segment because I'm a Japanese, and that's why my English is sometimes weird, hehe.
>Blue Oni Red Oni
I skip this spell most of the time because I'm quite bad at it for some reason.
Every time I fail, it greatly discourages me. And on that run, I focused to not die.