Merge is a block of code that allows you to optimize your game. in case of creating a game with many cubes or models it is recommended to put it inside the code block (merge).
PARAMETERS
Texture alpha:sets the opacity of all the code blocks that are inside the merge command
visibility:establishes the visibility of all code blocks within the command
Cast shandows:sets the shadows of all objects within merge depending on whether the material of the objects have effects by light, point light or directional light