Citadel

Citadel is a plugin (source) which allows blocks to be reinforced, making them hundreds or thousands of times harder to break. Reinforcements are tied to a Namelayer group and can be bypassed by players on that group. Many civ-specific blocks such as Snitches and Bastions only become active once reinforced.

Reinforcing
Reinforcing blocks costs one item of the corresponding reinforcement material. This item is returned only when a player who is on the reinforcement group mines the block or uses the relevant Citadel command. Choice of reinforcement material is selected by punching the block with a chosen item or using Citadel commands.

It is possible to double reinforce a double chest by placing it while using.

Insecure Reinforcement
A reinforcement can be set to insecure by using  or   and hitting it. This allows hoppers to move items in and out.

Unreinforceable blocks
Some blocks cannot be reinforced. This includes blocks with unique properties such as TNT, bedrock and portal blocks. Most plants cannot be reinforced. Liquids and entities are also not reinforceable, as they are not blocks.

Breaking


Whereas normal minecraft blocks need only be broken once to actually break, reinforced blocks must be broken hundreds or thousands of times, depending on the material used to reinforce it. Tool durability does not decrease when breaking reinforcements, only when performing the final break of a reinforced block which results in its actual breakage. This means that breaking a reinforced block costs only 1 durability from the tool used.

Explosions will do one reinforcement damage to all blocks in blast range. This only applies to blocks that the explosion would have been able to damage had they been unreinforced.

Acid Blocks
Acid blocks is a particular block (usually a gold block) which can be placed underneath a reinforced block to "dissolve" the reinforcement. Depending on the reinforcement material used, the acid block could take hours or days to mature and fully dissolve the reinforcement. As many acid blocks can be placed at the same time and they all mature at once, acid blocks can be much faster at breaking reinforcements in some circumstances.

To use an acid block, place the designated acid block type underneath a reinforced block, then reinforce it with the same material that the block you're trying to dissolve is reinforced with. Wait the designated maturation time, then come back, look at the acid block, and type  to both pop the acid block and break the block above it.

The  command has a range of 40 blocks and can be used to remove many acid blocks simultaneously, as long as they are all in line with the player's cursor when the command is issued.

Acid blocks are why almost all defensive infrastructure (such as Vaults and Bunkers) are built at bedrock: you cannot use acid blocks on blocks which are built directly on top of bedrock.

Acid blocks are often used to clean up Obsidian Bombs.

Decay
Reinforcements can decay if nobody on the group they are reinforced to logs in for a certain amount of time. For instance, if nobody on a group logs in for 3 months, all blocks reinforced to that group will get a damage multiplier of 2 (meaning they require half the breaks to break).

Since a single player on the group logging in is enough to reset decay, decayed reinforcements are uncommon.

Redstone Interactions
TODO rewrite as paragraphs


 * Reinforced buttons will only emit a signal if someone from the namelayer is nearby (distance?)
 * Comparators cannot inspect the content of a reinforced container block (e.g: chests, furnaces, droppers)
 * Droppers and hoppers will not transfer items if the destination block is not on the same reinforcement group.
 * Blocks can not be attached to a reinforced redstone component (e.g dropper, dispenser, hopper?) if not on the reinforcement groups.
 * Reinforced doors, trapdoors and fences gate will only respond to a redstone signal if someone on the reinforcement group is less than 7 blocks away from it

Advanced features
TODO clean this up, move to other sections


 * Note that reinforced blocks are not affected by gravity (e.g. reinforced sand will float). However if the block by default breaks when block beneath is removed, it will break even if reinforced (e.g. rails whose base is broken will also break).
 * Being in reinforcement or fortify mode will prevent the use of citadel buttons. Walking over pressure plates while in this mode will reinforce them to currently selected group.
 * Reinforcing farmland will give crops planted on it citadel protection.
 * Reinforce leaf blocks and destroying the tree they are apart of will lead to loss of reinforcment.

Known bugs

 * Placing a reinforced button/sign and breaking the block at the base will make it drop but will leave a reinforced air block behind. As this is an exploit its use should be avoided.