I don't get it.

white start with a horse, black starts with normal pieces, white plays 2 times, then black plays. Not hard?? But when white plays the first move with the horse it is already check mate.

yes, but what's the idea? ,and why can't you move twice at first?

The board only allows legal moves.

I'm going to sue the OP for 30 seconds.

The White Knight on d5 does not checkmate the Black King.  Unless it's some kind of super-Knight...

it takes the king on the second move

ah yes, I understand now, all those moves at first because you can't move twice and you want to, but I think the last position is enough to illustrate...

It does, since it can move twice, it plays Nf6 and takes the king, so therefore it's checkmate on d5.

Yeah, I know 

review "5000 sign you don't know enough about chess" and some puzzles there allow the king to move 2 squares and they even contain King-capture moves!! How can they do this?

You have to manually edit the PGN and write e.g. 1. Kxh8

wow, brilliant   ,isn't this better than the original one?

Just one question...so what?

...

You could say that the point is to show that tempo is more important than material. The one Knight that can move twice is enough to either checkmate the king or eat up all the material on the side that can only move once.

That and it's kinda funny.

An actual good example to show tempo is more important than material:

If white saves his bishop he only draws:

but those are praticular cases, so I don't agree, In the majority of position material is much more important than tempo.

btw the example above is very nice (well composed).

Yeah, of course.