Wizznic is a sliding blocks puzzle game. The game is written in C and used SDL and SDL Gfx. The developer a Danish programmer called Jimmy Christensen has made it freely available on GitHub so you can modify it, do what you want with it. It’s distributed under the GNU GPL (General Public Licence).
The game itself is multi level and there are other levels (DLC – free) available, just get the code on the content page. The game includes an editor which is why I guess there are so many downloads available.
The game itself is for gp2x, Windows and Linux and also includes make files for Pandora and PSP (PlayStation Portable). I’m always curious about the source code and the main game comes in 36 .c files and 37 .h with the biggest file being the 2000 lines of code menu.c.
If you are learning C or just want to see how a game is done, it’s an excellent way to study, especially because it’s cross platform. I suspect it’s SDL 1.25 because it uses surfaces rather than textures as in SDL 2.