I've tried for two days, anyone can tell me how to solve it pls?
That's not a colon
Usually best to stick to ascii characters in code. If you have other characters they probably belong in another file as data.
You can save your code as unicode, so if you really want comments or strings in Korean? then you can do that. I just can't recommend it from my own point of view, it's one more thing that can go wrong and there will probably be less people that will be able to read it.
Someone might for example want to view your code in a terminal and that terminal might only be able to display ascii characters. Stuff like that. My browser would only draw box characters if you wrote something in Korean - it's not configured to deal with that.
!!!!!!! yes! I just noticed I forgot to turn my input language to English....Thanks a lot! I changed the wrong colon and I tried one more time and it worked!!