Partially recreated below
HOW TO WATCH FLASH CONTENT
>Ruffle
>https://github.com/ruffle-rs/ruffle
This is an open-source emulator that parse swf files and displays them in the browser using JavaScript and WebAssembly.
Functionality is limited but can work decent on older flash files. If Ruffle seems outdated go tell me to update it in this thread.
Notably ActionScript 3 doesn't work with Ruffle yet, neither does blur nor glow filter effects.
>Projector
>https://www.adobe.com/support/flashplayer/debug_downloads.html
Adobe's offline Flash Player is still available for download on their site and it is what I recommend if you want a simple yet reliable way to watch flash files.
Save flashplayer_32_sa.exe somewhere on your computer (no installation needed). When asked what to do with the swf file you tell your browser to "Open with" the projector exe.
The flash will be downloaded to a temp location and then automatically viewed in flashplayer_32_sa.exe.
>Plugin
>https://ia803201.us.archive.org/view_archive.php?archive=/18/items/flashplayerarchive/pub/flashplayer/installers/archive/fp_32.0.0.371_archive.zip
Either install an old version of the official plugin or the last version (which is bricked by Adobe) and then replace it with a fixed version. Check here for resources and instructions.
With the NPAPI plugin you can view flash in your browser as long as it still supports NPAPI (
https://www.palemoon.org/). With the ActiveX plugin you can view flash with a seekbar in MPC-HC.
HOW TO MAKE FLASH CONTENT
You make it in flash! Adobe Flash CS6 Professional to be specific.
The only downside with CS6 compared to earliler or newer versions of Pro/CC/Animate is that CS6 can't import .svg vectors but you can use Inkscape to convert SVG into the supported .fxg format (Flash XML Graphics).
There's an old guide available on how to make a basic flash loop in CS6:
http://boards.swfchan.net/1922/