I don't think that the concept of "C" is as easy to grasp / natural as the circled numbers. There may be a special symbol (but not a letter) like spending snow mana (which is the closest thing in RL, but hasn't catched up as well).The reminder text should be below the activated ability.
I get the idea but don't like the C-circle. I admit to liking Unaligned (the flavor is nice). Anyone have a better idea?
I would use a different symbol if I could (a gear, maybe?), but the program I use to make these cards doesn't have the option to use homemade symbols. The hint I old like the most about that over Unaligned is he fact that you can cost a spell at 3cc instead of 5 with unaligned.