Some AI upscaled graphics?

I'm pretty sure its an artist redraw.

Back when Braid was originally being developed, with its launch platform being the Xbox 360, 720p seemed like a pretty high resolution. Neither the Xbox 360 nor the PlayStation 3 could render most games at higher resolution than that; a few games could barely do 1080p, if they were very spare with regard to per-pixel detail, which Braid was not (Braid's style involves drawing lots of translucent particles over each other, which means each pixel is drawn many times!). But when David Hellman came on to the project to do the game's visuals, we decided we would future-proof the game by drawing all the source art at twice 720p, then scale it down for the game's release. At the time, around the year 2007, this was difficult to do; the tools we were using would chug unresponsively when trying to edit such large bitmaps. But surely this would all be worth it, because it would allow us to re-release the game with sharper graphics later on!

We just didn't think far enough ahead, I guess; before too long, 4k monitors became available, some folks are using 5k monitors, and 8k is on the horizon (though that seems pretty excessive to me, right now!) If you play original Braid on a 4k monitor, the result is blurry and unpleasant to look at. The original double-scale art that we had archived for Braid would still be blurry at 4k, and anyway it was never really meant to be seen at that level of detail.

So, if we want people with modern computers to be able to enjoy the game the way it was meant to be played, how do we do that? Well, I guess the answer is for David to repaint the whole game at much higher levels of detail, so that is what we did.

http://braid-game.com/