Like said on Discord, I really like this Extra.
I think you went over everything that's needed to hack your own magic system into the game, and that's quite a challenge.
Magic is a wide term. It means a lot of things to a lot of different people, and each setting has its on twist on it. I think this should generally cover most use cases + it seems it ties itself very well into the core game mechanics.
Couple of things:
- Would it be worth mentioning that you could potentially use different actions to use magic within the same setting ? What you are describing seems to say "if you play with magic that works like this, choose an "action" to do magic. But I'm wondering if it would be interesting to also say that this "action" could also depend on what the PC is doing from one spell to the other? My concern is to have one "do magic" action though those concerns arent probably that important considering the cost and clocks mechanics you outlined
- Perhaps we could explain that the "magic charge / mana clock" could be tracked on the "projects & complications" clocks on the character sheet ?
- Another point we could touch on is "magic that trigers corruption" a la Fate of Chulhu. What do you think ?