Preview Window

When VZX is started, the preview window is at the top left.

To toggle rendering on and off, left-click the window and hit SPACE. This can be useful if you have accidentally created an effect which is rather heavy and you want to salvage it.
To show the output in full-window mode, hit Ctrl+F
When in full-window mode, hit Alt+F to enter "Performance mode" which overlays the module UI on top of the output.

Performance mode

When in full screen or full screen performance mode, hit Alt+T to toggle FPS and time information