I made one rather big app once .. that was my first B+ thing that had more than 20 lines of code .. after that I knew almost all ins & outs of B+ ..
Just make something useful, not 'big' by concept, but some small tool.. it'll turn out to grow big anyway :) That first 'big' app of mine was an image-converter that loaded bmp images with 16 colors, and the app included a palette-manager in which you could move around and modify some colors (with some simple RGB thing). Such a simple concept became many hundreds of lines..
Map-editors er even simpler to make if you already know some 2d commands & stuff..
Just make something useful, not 'big' by concept, but some small tool.. it'll turn out to grow big anyway :) That first 'big' app of mine was an image-converter that loaded bmp images with 16 colors, and the app included a palette-manager in which you could move around and modify some colors (with some simple RGB thing). Such a simple concept became many hundreds of lines..
Map-editors er even simpler to make if you already know some 2d commands & stuff..