Sudden Setback

What separates this from a straight counterspell or a straight bounce is the seam it sits on: it can catch a spell still on the stack or a nonland permanent already resolved on the battlefield, and it answers either by shipping it into the library instead of back to hand. That reach is what the double-blue commitment buys, and it asks more than a two-mana tempo play would. The concession that governs how much the card actually accomplishes is that the owner picks top or bottom. Against something the opponent wants back, you've bought a single turn: they send it to the top and redraw it, no better than a Time Ebb. The card earns its cost in the cases where the choice doesn't help, when the top of the library is as dead as the bottom, or when the target is a token, which ceases to exist the instant it changes zones no matter which end its owner names. Read it as a two-zone answer that trades the finality of a hard counter or true exile for the ability to hit any spell on the stack or nonland permanent on the board; the price of that flexibility is letting the opponent decide how far back the setback really sets them.