The program demonstrates the possibilities of a simple gui called GEM. A graphic and musical demo is to be made of this. 
I am asking for comments on what you can add, change …
NIKIFOR.7z (91.6 KB)
You can test SDL blend modes, you can also see the slowdown in Linux (the reason is the processing of more events?). Random generated patterns, you can also see the differences between win and linux …
The keys < > form a grid, the selected one can be enlarged after selecting the “Powiększenie” option, the block is cut with the ESC key