ooh i love how this one looks! i love when paintings have that liittle bit of roughness around the edges of its subject(s) (the cup in this case)

as for things of importance with shadows, in my observations, there are some things:

-the dimensions of the subject
-colors of the surroundings

the dimensions are of note because they affect the intensity of the shadows. the rounder something is/more of a curvature it has, the more variation there is in the shadows. (the more "half tone" or "areas between light and dark") it has)

it's like a sphere versus a cube, the sphere has way more variation in its shadows than the cube because the curvature of the sphere causes light to hit it differently-- less evenly.

color of surroundings is pretty simple. light reflects off stuff which, in situations with some very bright light in places (like the sun shining through a window into a room with no lights on) stuff can reflect almost like a weak flashlight lol.

--

and in other situations (being outside when skies are clear) the reflective/ambient light isnt nearly as evident as the example i mentioned in my 1st comment but it's still very much there.

next time youre outside when the sky's clear, do something to cast a shadow over something like your arm and look at the shadow, it'll have a faint bluish tint from the sky.

now, some colors show this more than others-- white or light colored things are affected more than dark colored things (since dark colors absorb light).

it's 4 AM and im half awake, i hope these text walls of mine arent hard to understand in any way lol.

Re: thank you so much!
Katt explained everything I would have and more xD

WOW thanks @Krazy Katt111. I really appreciate your thoughts and pieces of advice. I will definitively have it all in mind in my future work.

Will do @Maruka-Des. Thanks!