Hide and seek but you can morph into blocks

How it works:
A falling block summons at your position but then dies you have to hide somewhere.

The setup of command blocks:
So there are two command blocks that summon the falling blocks
The command for that is:

/execute at @e[​tag=hider] align xyz run summon falling_block ~0.5 ~ ~0.5 {NoGravity:1,Time:1,BlockState:{Name:"[​Block Name eg:oak_planks]"}}.

Then power another command block the command in it is:

/kill @e[​type=falling_block].

Then we have to give the hider invisibility so we do the command for that is:

/effect give @e[​tag=hider] invisibility 1 1 true.

And the seeker has to stay still and can't see.