The Duck Builder Simulation is a small game made in 2002 and was frequently used in schools.
The aim of the game is to adjust the ducks body parts to make it fly in a straight line. Too heavy and it will fall to the ground and too light would make it fly into space.
The only proof of the games existence i can find is a website made by Simon Haughton and 4 youtube videos.
There is a download link on the website but it just leads to an error screen and using the Wayback Machine also doesn't work.
The only way i can see this game being found is if someone who had downloaded the game when it was still up comes forward and uploads the game to archive.org
or somewhere else.
I did play this game alot when i was in school almost 10 years ago so it would be really nice to play it again.
If the game is notable enough for an article, create it and call the page something along the lines of "The Duck Builder Simulation (lost video game; 2002)" (if you come up with a better title call the page that).
There is also 2 versions of this game, a beta version and the final version. i remember playing the beta version as the videos show the final version which has a more detailed background in the testing ground segment. the beta version has a very basic background.
So, I attempted a basic search on Google. What I found was your Reddit post on r/lostmedia, the TypePad site that you linked to, and a fake download that was supposed to be the game. I did also find creator Simon Haughton's official site:
At the bottom of each page, is a link to his Twitter and an email address. I don't have Twitter, but I did send an email, so now we'll have to wait and see how long it takes for/if there's a response. Until then, I will continue to help searching and see what else we might possibly turn up.