Photosynthesis: Under the Moonlight is what you should expect out of an expansion as it adds some interesting new mechanics to the game without interfering with what made the original so enjoyable in the first place.
Photosynthesis is arguably the best blend between a theme and gameplay that I have ever seen which leads to an original and really fun experience that is a delight to play.
Abalone is a solid abstract strategy game that is simple enough for the whole family to enjoy which unfortunately has a potentially fatal flaw that has to be addressed in order to truly enjoy the game.
Blokus 3D may be part of the Blokus franchise and share some things in common with other games in the franchise, but by adding the third dimension it creates its own unique game that fans of abstract strategy games should enjoy.
LEGO Harry Potter Hogwarts has some interesting ideas that should appeal to children, but too many of the mechanics don’t work as intended leading to a boring experience for adults.
Blokus Trigon doesn’t drastically differentiate itself from the original Blokus, but it maintains the simplicity and fun of the original game.
Hexagrams has some interesting ideas that unfortunately don’t really work leading to another pretty bland and boring Checkers spinoff.
Tank Battle is an interesting combination of Battleship and Stratego that you can have some fun with even if it ends up becoming a basic guessing game.
I don’t think Santorini lives up to all of the hype surrounding the game, but it is still one of the best abstract strategy games that I have ever played.