Like others here, I found Powder Game through NotDoppler. I played it for several months and frequented the comment board. There was a debate raging over PG vs. TPT. I had no idea what TPT was, so I googled it and downloaded the original. I still have a copy of that somewhere.
I had fun with it, but eventually got sick of the limited element selection, and decided to check for an update. This was when the server was down, so I forgot about it for a while. Later, I was curious as to whether anyone else had uploaded a copy of TPT, and found this site.
I had to use the copy from geeks3D for a while because powder.unaligned.org went down, and I could not find powder.hard-wired.org.uk until I found powder.co.uk through facebook.
Initially, I read about TPT in July 2011 issue of Linux Format magazine. I was looking for some good sandbox game, and TPT sounded like a really great project, so I checked it out... That was about version 46-49. And since that, I was playing TPT and I still play it. It was exactly what I was looking for. I made some friends interested in TPT. Nowadays, when I play TPT in public, I make sure that people can clearly see screen and if they ask about it, I give them URL to this site.
Interestingly, when I first played TPT, something felt like another game I played - real-time worms game Liero-AI by Stanislaw K Skowronek (perhaps, it's water and particle simulation). I was quite surprised, when I learned, that originally TPT was made by same person.
Falling sands.
I first played Falling Sand then Powder Game then Owen Pieties Desktop Falling Sand game for two years, I made a mod for it but it got boring quite quickly, I searched around and found Powder Toy and downloaded it, it wasnt until later that I actully started playing it, for the last 3 and almost 4 (I remember starting playing it in November) now, I am less active on the game but still requarly go on the forums.
A random kid in my art class was blowing stuff up in tpt.