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Hmm... I work professionally with Photoshop, but I still love and use Paint... for example, to save a screenshot or to sketch on a tablet, just for fun... Paint is a universal tool! It even has a transparent background... I still have some of my drawings from back then, when I had a small, old computer with a tiny display, and I couldn't even dream of Photoshop... it was around 2001, I think, so I was about 14 years old... this is what I used to create... :)
P.S. I'm teaching my friend's daughter how to use a computer - she's little and wants to draw, so Photoshop is too complicated for her right now, but she enjoys drawing in Paint and does it very well... for a beginner, it's a treasure... :)
Regarding what you posted - it's great! But I think that now, knowing the laws of color and painting, I could repeat something like that or create something similar... of course, with a graphics tablet... in the video, they clearly didn't just use a mouse...