Cave-In deals 2 damage to each creature and each player, which cleanly kills their 1-toughness mana dorks like Birds of Paradise, Llanowar Elves, Squee, Goblin Nabob, and Sylvan Safekeeper, while also hitting our own small creatures, so sequence it to maximize their losses. Mana Leak is a liability against a deck built around Survival of the Fittest, Weathered Wayfarer, and cheap efficient threats that doesn't lean on hard-to-pay spells, since they can often find the mana to push through. Watch out for Armageddon, which can blow up the board state in their favor if they're ahead on board; try to hold mana open or keep threats that don't need much support. Keep Survival of the Fittest and our core creature base to grind through their removal-light, value-oriented game plan.