Yuki Fujimoto has produced a lot of pencil puzzle apps recently.  Sun or Moon is also known as ????. 
  1. The object is to create a single loop that will pass through every country. The yellow lines are the borders of those countries.
2.  Within each country, the line/loop can only pass through a Sun or Moon.  When going from country to country, the sun & moon must alternate.  Also, within a single country, you can pass through multiple suns or multiple moons, but not both.
I like this game a lot.  I did all the 5x5 grids quickly, then jumped to the 10x10 levels.  And that's when I noticed a bug in the program.  No matter what loop I draw, the program says I've solved it.  Oh well.  It's still a good game and you know when you've solved it or when you're stuck.
https://itunes.apple.com/jp/app/yueka-tai-yang/id1175901385"mt=8

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