Sometimes the biggest challenges come from games with very few rules. It's the principle behind Simple Machine's latest puzzle, in which you combine matching numbered tiles until there's only one. It's simple, it's clever, and it's difficult in the best of ways.
There are a lot of solitaire games out there, so it's really rare to find one that stands out. 4 Thrones is one of those rare games. While at first it seems like a simple sorting game, there's a lot of strategy involved in this unique take on the genre. And it lends itself to imagining the face cards as real kings, queens, and princes, which is always a plus.