I'm giving Worldoku a shot. I'm fairly familiar with country flags, if I may say so myself, as I play Flagle, Worldle and Geozee. And I'm no stranger to Sudoku and Murdoku either. And yet I find this is breaking my brain somehow and I'm struggling a bit to keep the board's state in my head. Maybe I just need more practice.
I do love the concept and I'll try playing more than one assuming I can finish the one I've started. :)
The game is really cool, but it allowed me to cheat on mobile when asked for coastal lines: it shows the actual coastal line for a second, then draws the rest of the map over. Also, it said Belgium is landlocked.
I created "Borderline", a border drawing game a few weeks ago.
Since then, thousands of people have played it and I have accumulated over 37,000 drawings, which are now all stacked on a blank canvas.
This allows you to see the world as people remember it.
You can also check similar maps for the US, France, the UK, Germany, Australia, and Switzerland.
Alternatively, you can also draw a few borders yourself (free, no signin required)