This looks really good. It correctly allows for negative numbers i.e. you can write -5 * 4 or 5 * -4 and it will give you -20. It allows for operator chaining successfully. It also looks visually nice and thematic.
There are a few bugs/flaws you might want to look into.
Second, while you do have input overflow controls for the top row, the bottom row overflows when chaining together a bunch of operations.
There are also some logic flow issues with button presses. Take CE i.e. clear entry. For example, if I press 12 + and then press CE to get rid of the +, the top row then displays 0 rather than 12.
Also, there are some issues with the decimal point. Your calculator allows for 4 / . + and I assume you don’t want to allow an isolated decimal point by itself.
Finally, when I just have 0, I am allowed to write 0 + 4, 0 - 4, and 0 / 4, but for some reason I can’t write a * after the initial 0. You might want to look into that.
But on the whole, well done and it works quite logically.