Cooka is a very simple image viewer written in C# (less than 900 lines of code, comments included) and compiled with Mono framework. The application is really essential: it has a file system browser in order to select the folder containing images to display; a thumbs viewer useful to see a preview of the images within the selected folder and some information like image's name, size and dimension; and finally a "view" area used to display the selected image.
In order to handle images and to enhance image viewing, Cooka provides a simple toolbar that allows users perform some basic operation such as rotate, zoom, set as background.
But, why Cooka is an old style image viewer ? Simply because it's possible to hide all the "interactive" areas (using keyboard shortcut) and focalize your attention on image. All the actions will be performed using your keyboard.