Do you know of anything like AoC but that feels less contrived? I often spend the most time understanding the problem requirements because they are so arbitrary - like the worst kind of boardgame! Maybe I should go pick up some OSS tickets...
Just a random example: https://open.kattis.com/problems/magicallights
But the Kattis website is great. The program runs on their server without you getting to know the input (you just get right/wrong back), so a bit different. But also then gives you memory and time constraints which you for the more difficult problems must find your way out of.