Helpmate in 4

Check out this puzzle I just created! Helpmate in 4: black moves first, and helps white checkmate him on the 4th move!

en.lichess.org/analysis/K5B1/8/4R3/3k4/b7/4n3/4P3/8_b_-_-

You'll have to flip the board to see it from white's perspective.
Also, I didn't check it for other solutions yet.

How difficult was it?

there is a helpmate in 3

What's a helpmate?

Not as beautiful, but fixed. Helpmate in 3:

en.lichess.org/analysis/7K/7B/4R3/3n4/b2k4/8/4P3/8_b_-_-

This is where black and white work together to get black checkmated in the specified number of moves.

Solution:

1. Bd1! Rg6
2. Ke4 e3
3. Bf3 Re6#