I have no idea what Curve is doing on this card. Is it supposed to be "Three additional permanents"?

It works the same, but proably should edit the wording (As you would get to target another three permanents), but its confusing because of the wording i use on most of the other curve cards. Change made.

How about "Curve 3... you may tap up to an additional three target permanents"? It'd be fiddly on MTGO, but otherwise work okay. This wording with "Instead" is fine too though.

Is "Up to an additional" correct? If it is then its a cleaner version and i will change it.

There hasn't been anything printed with quite that wording. I think it'd work. Anyone else who's skilled in templating care to contributed?

This is why kicker spells and the like never actually change their targets in upgraded form. They can change what happens to those targets (Vines of Vastwood), do something extra that isn't targeted (Agonizing Demise), or effectively render the target irrelevant (Epicenter), but apart from multikicker cards like Comet Storm that obviously don't cause confusion over "Do I get to/have to choose the additional targets if I'm just using the vanilla form?", they deliberately don't allow that question to arise.

Well, that's not really true. Orim's Thunder, Jilt, and so on gain additional targets if kicked. The Comp Rules support that:

> 601.2c ... A spell may require some targets only if an alternative or additional cost (such as a buyback or kicker cost), or a particular mode, was chosen for it; otherwise, the spell is cast as though it did not require those targets.

Curve isn't quite an alternative mode, but it's pretty similar. In order for this card to work, they'd probably have to make a minor alteration to rule 601.2c.

How about: Target up to six permanents, tap up to three of them. Curve 3: Tap all of them.

That general approach does work. It's just... ugly design. It does a variety of fiddly things that are generally against design principles, particularly for a common utility spell, like letting you target more stuff than you can target and leaving the opponent to guess which ones you're actually going to tap.

Now if you wanted to make a cycle of spells that deliberately did that, as their thing, that'd be kinda cool. "Choose two target creatures. ~ deals 3 damage to one of them." Which one do you use your pump / damage prevention on? Etc. But it's odd enough that it should be on something that's explicitly doing that as its thing, not thrown in to another card as a consequence of templating difficulties.