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.
Black-Pearl Flower
100 Games
Black-Pearl Cluster
75,000 Points in Timed
150,000 Points in Marathon
1,000,000 Total Points
5000 Total Combos
Beat Survival
Black Pearl
Starflower
Bonus-Star Cluster
25 Total Combos