Here is the full list of all 12 Hexic HD achievements worth 200 gamerscore. It takes around 20-25 hours to unlock all of the achievements on Xbox 360.
25 Total Combos
Bonus-Star Cluster
Starflower
Black Pearl
Black-Pearl Cluster
100 Games
5000 Total Combos
Beat Survival
75,000 Points in Timed
150,000 Points in Marathon
1,000,000 Total Points
Black-Pearl Flower