Colorless Prison leans on cheap artifacts like Lotus Petal and Grim Monolith to power out Karn, the Great Creator and The One Ring, while Trinisphere taxes our cheap spells. Meltdown is a powerful sweeper that can blow out multiple mana rocks or Trinisphere at once for a well-chosen X. Ratchet Bomb can be set down early and ticked up to answer Trinisphere or Karn, but it has to be activated before Karn resolves, because Karn stops activated abilities of our artifacts. Once Karn is out the Bomb is stuck, so deploy it early. We cut Spell Pierce since their payoffs are often too expensive to be Pierced effectively, and Unholy Heat since it can only hit creatures or planeswalkers while most of their threats are artifacts. Into the Flood Maw stays in: if we promise the gift, it can bounce any nonland permanent, including Karn or Trinisphere, at the cost of giving them a tapped Fish. Keep Wasteland maximally active against their Urza's lands to slow their explosive starts.