The engine was rewritten to work with OpenGL instead of SDL, so there are still some bugs which may cause the game to crash and such.
There are four new levels with a variety of new encounters compared to the last demo.
Demo works only for 1920x1080 specifically tailored to work with only one type of PC (mine). In your feedback, it would be useful if you could provide some relevant details on your hardware (e.g. if it runs slow) and system (e.g. some weird graphical issues).
To toggle on/off the full screen press 'j'.