General advice: don't run batch scripts without opening them and reading what they do first.
I used "convert_bitmap8.bat". Place your .bmp files in the "bmp" folder. It will create the files in the "bitmap8" folder; there should be 2 of interest: <your_name>.img.bin and <your_name>.pal.bin...
I forgot there were releases there, last one was 2014 though. It does in fact include grit, the batch files, the PDF version of the documentation and even desmume.
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https://sourceforge.net/projects/nflib/
They were removed from the GitHub at some point. Here's the old version though. I highly recommend at least comparing the batch files to the grit documentation to see what is actually happening.
So glad I archived that PDF, the person who's been maintaining nds_nflib apparently removed it from the github a few months ago. The repo is setup so if you clone it and have "Doxygen" installed, you can generate documentation in HTML format. This guarantees the documentation is always...
I made an account years ago, but never used it unless a thread came up on Google. I recently completed a DS homebrew project so I have a little expertise that I can share with nflib and libnds. I figured participating in the forum is easier than trying to advertise my website and hoping that...
NF_WriteText(1,1,(SCREEN_WIDTH/2),SCREEN_HEIGHT - 16, "Welcome To Superball");
This function doesn't use screen coordinates. Try something like NF_WriteText(1,1,3,3, "Welcome To Superball"); to see if that is the problem.