How in earth is this checkmate ?
Ninja rook?
This says to me: stick with online chess ONLY
Your last move was notated as Kxa4 so Ra1# was mate.
Your screenshot is terrible on my screen. This is what your game shows as the ending: You just got mated.
My screen shows white king at b2. Blacks @ c4, with (black) rook @ a1
So, if my screen's working right, you posted the wrong emphasis.
mother of god