Technical blocks are blocks that cannot be achieved legitimately and serve a purpose in events in the game.
These blocks serve a purpose when a piston is used.
Block 34
Block 34 is a block used by the piston's extension arm.
Block 36
A comparison between a normal stone block, and a stone block with a block 36 on it
Block 36 is a block used by pistons, it is a side effect of the method of storing moving blocks as tile-entities instead of entities. This block's color, when located next to a block in the world, is black, but when a block next to it is removed it become invisible, it can be walked through, and when light pass through it it decreases the light level by 1. They are unbreakable in traditional ways; however, can be removed by right-clicking. The game treats the block as stone when it comes to braking animation and step sound. In the inventory it has a top of grass block texture in 2D grayed out for biome reasons and can't be placed.
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