@snake game That's also what makes these browser games so appealing: they're easy to pick up, don't require a big time commitment, and offer plenty of replay value. Good gameplay doesn't always need to be complicated.
If you want to be able to press a button that will capture a clip of what has just happened, you need to be already recording in order to do that. There is no way to save a clip if you were not already recording.
You can set the hotkey to save a clip while recording on the Hotkeys tab of the Settings and you can set the duration of the clip in the Options tab of the Settings.