Hi, MixEmergency doesn't directly support crossfading the video witht the left and right arrow keys. There is a feature that will allow you to trigger the autofade via a global keyboard shortcut though (this way you can do it no matter which application has the keyboard focus). To set this, go to the Transition section of MixEmergency's Preferences. There is a box titled Auto-fade, and within this, a control labelled Hot-key. Click this, and then record a new keyboard hot-key (usually I use something like control-option-command-space so that I can just push the bottom line of keys easily).