Oops, All Spells! is a turn-1 combo deck that wins by milling its entire library with Balustrade Spy or Undercity Informer, then leveraging Narcomoeba and Boggart Trawler triggers to assemble flashback fodder for Dread Return, ultimately winning with Thassa's Oracle on an empty library. Leyline of the Void is your most critical sideboard card — if it's in play before their combo resolves, every milled card is exiled rather than placed in the graveyard, completely shutting off Narcomoeba, Boggart Trawler, and Dread Return and leaving them without a win condition. Pithing Needle naming Undercity Informer removes one of their two combo routes, forcing them to rely solely on Balustrade Spy. Your four main-deck Pyroblast plus the additional Red Elemental Blast from the sideboard are your primary interaction, capable of countering Pact of Negation, which is the blue instant that protects their combo from disruption. Trim cards that do nothing against a non-combat, non-artifact combo deck: Ensnaring Bridge is irrelevant since they don't attack, and the slower value artifacts like Sewer-veillance Cam and Chaos Defiler won't affect the outcome of a race this fast.