A game will be captured only if it uses OpenGL, else nothing will be recorded.
Sound will be recorded only if the game uses ALSA. If it uses OpenGL, a video of gameplay will be still captured, sans any audio.
Choosing a game executable file is recommended way of capturing.
You can select one of your installed games in dropdown list, if it complies with first two requirements. However, this method can fail sometimes.
Hotkey defined in application can stop, pause or re-start recording.
Pressing a hotkey or clicking on stop action in indicator will only work if the game running in window mode has focus. In case of fullscreen mode, hotkey will work as expected.
If you disable option to start capturing video as soon a game initializes, use the hotkey to manually start recording while in game.
Once the recording has finished, you will get a .glc file which can run into lots of GBs even if you recorded game only for a couple of minutes. This is normal.
You can use play option to check your recorded file before encoding.
In playback mode, you can use ESC to stop playback, F to toggle fullscreen and Right Arrow key to seek forward.
Set number of threads to 0 in encoding options to automatically select optimal configuration as per your system.
All the required files including your final encoded video will be stored in working directory.