- default : the audio/track/music/video inside 'track_holder' would play one after another
- random : the audio/track/music/video inside 'track_holder' would play tracks randomly
- reverse : the audio/track/music/video inside 'track_holder' would play starts from last_track to first_track
- repeat : the audio/track/music/video inside 'track_holder' would play itself repeatedly and doesn't play another audio/track/music/video (similar to idle : repeat)
- none : if track_holder was empty, The current audio/track/music/video wouldn't do anything
- default : if track_holder was empty, The current audio/track/music/video will play another track next to it
- random : if track_holder was empty, The current audio/track/music/video would play track randomly
- reverse : if track_holder was empty, The current audio/track/music/video would play another track next to it in reverse
- repeat : if track_holder was empty, The current audio/track/music/video would play itself repeatedly and doesn't play another audio/track/music/video (similar to mode : repeat)