A classic... as someone who played the Atari version, it's just as I remember. Only thing... when you fire and then move the plane, the shot moves with you.
Duel Gem Mastery makes it so when you combine gems of different colors, IE, make a duel gem... (two different colors), that the damage and special reduction is smaller. Actually, having full duel gem mastery would make duel gem towers stronger than pure towers.
In short, Duel Gem Mastery makes duel gem towers strong.
That's not a refining glitch... lv10 refine has a 23% chance on easy. Which is rather small. And refining up to lv9 first doesn't improve it. If you want lv10 refined, buy the weapon and refine straight to 10.
I love the idea, and the drawings are great. However, it could use more content, IE, more classes, cards... and easier ways to get them, like, some sort of story mode or perhaps trading Badge points? Overall, it's fun. 4/5
 "Maize Maze")
 "Rage 3")
 "Gravity Master")
 "River Raid")
 ":the game:")
 "GemCraft")
 "Feudalism II")
 "Kongai")