This player is a valid single-file HTML app. It starts with the provided video URL and also accepts any direct URL pointing to an MP4 file.
Current source
https://producingtechnology.com/video/video.mp4
Type check
MP4 URL detected
Playback status
Ready
Bonus behavior: the app accepts other MP4 URLs too. It checks whether the entered URL appears to point to an .mp4 file before loading, but still lets the browser make the final playback decision.