Oh sorry I forgot to mention it in the readme, you have to call SLX3SwitchResolution(var_videomode);
before the video_switch();
var video_mode is the same.

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com