Block Swap

Block Swap lets you place a block directly onto one that is already there. The old block pops out as a drop and the new one takes its tile in a single click, instead of the usual mine, wait, place cycle. It is a toggle that sits with the other build options beside your inventory, and it stays on until you turn it off.

The saving looks trivial on one tile and enormous over a wall of a few thousand. Retexturing a house, converting a mud tunnel to brick, or pulling an ugly stone patch out of a finished build all go from a two pass job to one pass, and you never leave a hole open while you work.

Swapping is not a way around mining power. The game runs the same check it would if you were breaking the block normally, and if your tool cannot handle the target then nothing happens at all.

One threshold exists specifically for swapping. Gravity affected blocks like sand, silt and slush can only be swapped from the topmost block downward while you hold anything under 110 percent pickaxe power, which means anything weaker than a Cobalt Pickaxe. At or above that figure you can swap them anywhere in the pile. Trading one gravity block for another ignores the rule entirely, whatever you are holding.

The exclusions are not arbitrary. Most of them exist because a swap would let you skip something the game wants you to actually deal with.

• Furniture, with a short list of exceptions. Campfires can be swapped for another campfire and always come back lit. Unlocked Chests can be swapped and keep their contents. Torches keep whether they were on or off. A Dead Man's Chest will fire its wire signal when swapped, so that one is not a free defusal.
• Blocks holding up a tree or a fallen log. Otherwise you could quietly replace the ground under a tree without it noticing.
• Grass going back to its plain counterpart. Corrupt, crimson and hallowed grass will not swap to Dirt, and jungle or mushroom grass will not swap to Mud. Those have to be broken.
• Hive. A Hive Wand can swap hive in, but nothing swaps it back out again.
• Bubbles and Hellstone, along with Smoke and Living Fire blocks.
• Single floating walls with nothing connected to them.

Several long standing annoyances stop being annoyances once the toggle is on.

• Ore hanging over a drop. Swap the vein tile by tile and you never lose your footing, because there is no moment where the block is absent.
• Chlorophyte Ore. Swap it for mud and you collect the ore while leaving behind the mud it needs to regrow, which turns a one time deposit into a renewable farm.
• Altars. The blocks under a demon or crimson altar can be swapped without the altar breaking, so you can lay a proper floor beneath one instead of building around it.
• Lava. A block touching lava can be swapped, which lets you seal a pool from the safe side rather than digging in next to it.

Neither of the ore tricks counts toward the mining achievements attached to those ores. Nothing is technically being mined, so nothing fires.

• Paint and coating on the old block are lost. If you have sprayed a section and then swap the blocks in it, expect to repaint the lot.
• Swapping an actuated block leaves the new block actuated too. Usually that is what you want, but it does mean a block you thought you placed solid can turn out to be one you walk straight through.