Re:Ask HN: What website, from your early days on the net, do...
by personlurking on Saturday April 25, 2020 @11:26PM
(#22984121)
When I look at the Archives on Project Euler, the same general idea is there but the site I miss wasn't programming focused. I seem to recall a giant red, blue or green background and the puzzles weren't just text-based, but visual.
https://projecteuler.net/