SMILEBasic is a 3DS application that lets you run their own flavour of BASIC called SmileBASIC. It's a pretty cool language, and might have some potential for code-golf, but I don't think a lot. The issue in measuring its source-code stems from the fact that we don't know if SmileBASIC saves its programs in UTF-16 or UTF-8 (because they're saved somewhere within the SmileBASIC application's save-data).
This answer has a comment thread discussing SmileBASIC, and how to count the bytes. We see here that SmileBASIC certainly encodes at least displayed strings as UTF-16, but is that enough to say the source code is also in UTF-16?
Here we have a list of every single SmileBASIC instruction. You'll notice all of them are actually ascii, and don't utilise any of the extended symbols presented by the SmileBASIC UTF-16 encoding. Looking closer at the file instructions you'll see that
SAVE (2) Saves a string variable to a text file actually saves in a UTF-8 encoding:
SAVE "TXT:File name", String variable
Arguments File name Name to save the file under (prefixed with "TXT:")
String variable String variable containing the text data to be saved (UTF-8)
So what should we measure SmileBASIC as? UTF-8 or UTF-16?