Blue Elemental Blast and Hydroblast are premium answers here, countering or destroying Fiery Temper, Lightning Bolt, and the deck's red creatures like Kessig Flamebreather and Guttersnipe before they trigger madness damage. Trim slow or clunky cards like Faerie Seer and the single Thorn of the Black Rose since this matchup is a race against a fast damage clock, not a grindy value game. Keep Snuff Out and Counterspell fully intact as your main lines of interaction against their burn and creatures. Prioritize killing Guttersnipe and Kessig Flamebreather on sight since they turn every subsequent spell into extra damage.

Spreading Seas blanks their non-basic lands and replaces them with an Island, slowing their mana and hurting any colored requirements while replacing itself with a card. Relic of Progenitus can exile their graveyard to shrink Tolarian Terror and Cryptic Serpent's cost reduction, providing a repeatable tap ability to exile cards in addition to its one-time sacrifice activation. Cast Down and Suffocating Fumes are weak since Tolarian Terror and Cryptic Serpent are their main threats and get big fast, but Agony Warp and Echoing Decay remain fine cheap answers to Delver. This is a fair blue mirror where card advantage and countermagic matter most, so keep the full Counterspell and Spellstutter Sprite package.

Tron aims to assemble Urza's Tower, Urza's Mine, and Urza's Power Plant to cheat out huge threats like Bramble Wurm and Nyxborn Hydra, so countermagic like Counterspell is premium to stop these bombs before they land. Nihil Spellbomb and Relic of Progenitus give some graveyard disruption against their Ancient Stirrings and Crop Rotation-fueled recursion plans, and are cheap enough not to slow you down. Suffocating Fumes' -1/-1 doesn't meaningfully answer their large creatures like Bramble Wurm, so it can sit. Prioritize countering their bomb creatures and removal-resistant threats since Tron games are often decided by a single huge spell resolving.