Can I also use "shining" instead of "shiny" here?
You may be able to, but I don't think so. "It's so shiny" and It's shining" mean different things. "It's so shiny" means that this golden egg is reflecting light very well. "It's shining" means that this golden egg is emitting or giving off a bright light on its own. Since this is an animated video, the egg may be giving off a bright light on its own, but since she uses "it's shiny," I'm assuming she means that the egg is reflecting light. Ex: The shell is so shiny! Ex: The sun is shining off the lake. Ex: I can't believe how shiny your car is.
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