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They do each color has to have a unique rgb value when drawing it (You can add a few more shades later in development with alpha channels)

It is technically allowed but as you said it will be hard without knowing what the theme is but I guess you could always come up with a basic idea and then modify it based on what the theme is. 

it only works on windows and linux

Thankyou

If the programmer is under 18 but the artist is 20. Can the game still qualify for prizes?

C# is pretty hard if that didn't work out next time you can try python with pygame because that's way easier or if you want a simpler game engine you can use GDevelop.

I am

this is a really god tileset

I liked it