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