Bubble

Bubbles are animated background furniture blocks, which have special behavior regarding liquids, interacting as if the bubble was a solid block. When bubbles are placed together in groups, they connect to make a larger bubble or more complex structures.

Bubbles are purchased from the Party Girl for each, after the world enters Hardmode.

Grates function as the opposite of bubbles, acting as solid blocks but allowing liquids to flow through.

Behavior
The only blocks that can be attached to placed bubbles are other bubbles (unless there is a background wall present). Bubbles cannot be hammered into half-blocks, and are thus unable to produce Waterfalls. Actuators do not affect bubbles.

Liquids will collide with bubbles as if they were solid blocks. Structures made of bubbles can be used to contain liquids just like blocks. Bubbles can also keep liquids "inside" them, just as solid blocks can trap liquids they were placed over. The liquid cannot be seen inside the bubble, so empty bubbles and filled bubbles appear the same, however it can be interacted with:
 * If you use bubbles to create a Lava pool, coins and other burnable objects will be destroyed when contacting the Lava, no matter how thin the Lava is. This may be because instead of "hitting bottom", items pass through the bubble floor, until they are deep enough in the lava to burn.
 * Clicking on an empty bubble with a full Bucket will place the bucket's contents into the bubble. The liquid can be removed again with an empty bucket. Removing the filled bubble (e.g., with a pickaxe) will free the liquid, causing it to fall (or react with other liquids).
 * Each tile of bubble holds its liquid separately; even if the bubbles appear to be joined, the liquid will not flow among them, nor interact with liquid in other bubble tiles. A 2x2 bubble square may look like a single larger bubble, but it can hold water, lava, and honey in separate tiles without letting them react.
 * Bubbles with a liquid inside of them will act just as if they were their respective liquid. For example, it is possible to swim and drown in a water filled bubble.
 * Liquid in bubbles can react with a (slower) "free" liquid above or next to it. This will always consume the entire contents of the bubble tile, and however much was in the other tile.
 * Liquid stored in bubbles will be released (and allowed to fall) when reloading the world. (So care should be taken when storing Lava in bubbles.)
 * Liquid that is supported/confined by bubbles (but not contained in bubble tiles as described above) will remain in place.

Tips

 * Once placed, surrounding blocks and background walls can be removed, leaving a free-standing bubble.
 * A liquid-filled bubble and a Liquid Sensor can be used for a "reload detector", allowing complex circuits or machines to be restarted on world load. However, the bubble will need to be manually reloaded before the next restart.
 * Honey-filled bubbles are perfect for honey buff pickups for arenas.
 * Care should be taken with setting lava traps for flying enemies, as the Lava will kill flying Critters as well. Water will give players the "wet" buff when mounting Cute Fishron, if the player makes several bubbles of water around their world, they could be able to travel at high speeds using the Cute Fishron.
 * Players can walk on Water-filled or Honey-filled bubbles using any Water Walking Boots.
 * In adventure-themed Terraria maps, bubbles can be used as a filter to any liquid, including lava (for any particular part of the map where you have to get away from an incoming lava stream).
 * Liquid stored in a bubble can react with a different liquid that comes into contact with the bubble, producing the contact-created blocks (Honey Block, Obsidian, or Crispy Honey Block):
 * The slower-moving liquid can be poured over the bubble containing the faster liquid., producing a block next to the bubble. (Honey is slower than Lava, and Lava slower than Water.) The bubble will be emptied, but not all of the poured liquid will be consumed. The poured liquid must be the slower one; if, say, a water bucket is poured over a Honey-filled bubble, no block is created, and no liquid is consumed.
 * If two adjacent (side-by-side) bubbles are filled with different liquids, then a pickaxe can easily remove the Bubble with the slower-moving liquid. An appropriate block will be crafted. consuming both liquids. For example, if one bubble is filled with honey, and an adjacent (to the left or right) bubble with water, and the honey-filled bubble is then removed with a pickaxe, a Honey Block will be crafted.