What do people use these days to tinker with flash animation?

[Asterra]

This is surely the most newbie question I've ever asked. I can recall using an app for this, literally years and years ago. I don't remember the name of the app but it surely wasn't something made by Adobe and costing $600. I was hoping the answer to this would have been as simple as a quick Google search but it seems not to be as easy as that. I want to open some SWFs and mess with them. Where do I start? Thanks. ;p

[smrpix]

Since .swf can contain anything from simple video files, to elaborate instructions and functions, to external references, to any combination of the above it is complicated. On top of that Adobe's product is being deprecated in favor of Adobe Animate which supports more formats.

You can get a 30 day free trial of Flash (and it's $20/mo thereafter) directly from Adobe.

Or try this:
http://alternativeto.net/software/adobe-flash/

[Asterra]

Since .swf can contain anything from simple video files, to elaborate instructions and functions, to external references, to any combination of the above it is complicated.

I can narrow it down, at least. The SWFs I want to open are self-contained (as far as I know; at most, they may reference some local visual assets) and are simple, looping animations. Not GIF-style but more of the sort you get from drawing graphics in something MSPaint-like.