This app was mentioned in 7 comments, with an average of 1.71 upvotes
"Original mahjong" is kind of like saying "original poker" - it's virtually all variants. That said, the best and closest to "original mahjong" and a frequent starting point is Hong Kong Old Style. (I think Chinese Classical is closer to whatever "original Mahjong" is but most people suggest starting with HKOS)
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I don't know about flash apps, though they're probably available, but an Android app can be downloaded here-
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https://play.google.com/store/apps/details?id=com.pvella.mahjong&hl=en_US
I havent had enough time time to actually try it out yet, but I was hunting around and found one last week - It's annoyingly difficult to find them, sadly.
https://play.google.com/store/apps/details?id=com.pvella.mahjong
This looks legit. App is in English.
https://play.google.com/store/apps/details?id=com.pvella.mahjong
It depends which link you want and what platform...
Original versions
https://play.google.com/store/apps/details?id=com.pvella.mahjong
https://itunes.apple.com/us/app/hong-kong-style-mahjong/id916388468?ls=1&mt=8
New Versions in development
https://play.google.com/store/apps/details?id=com.pvella.mahjong3d
https://itunes.apple.com/us/app/hong-kong-style-mahjong-3d/id1457395895
Ok so a lot of comments are spread out with their resources. This is what I did to learn, in this order.
This is the best video there is. Not very many videos can be found on Chinese variants of the game. Watch it here. EDIT: This one helped with the BARE basics here
That video is not the best teacher there is, but you wanted a video. Hopefully that video will be enough to at least make you not confused when reading the rules here. If you're just starting you can ignore the part about breaking the wall and seating arrangements. Later on you'll have to learn them, but for now it should be very casual and simple.
If you have an android device, or any device that loads google play apps, get this one. I prefer this one since you can set the minimum fan (points) to go out on a hand, so it's good for beginners. The website itsmahjong.com requires a minimum of 3 fan, so go to that one once you get more accustomed to the rules.
It's a bit of a learning curve for new players, but just keep playing and you'll get the hang of it in no time! :)
Feel free to ask questions! Either I and/or the whole mahjong community will be more than happy to answer them. Have fun and keep playing!
EDIT: Added video