I noticed that this is a jar file, thank goodness I have Java installed in my device

As for the gameplay, there's an exploit wherein if you go out of bounds, i.e., off screen at the left, you'll be able to score endlessly (I think there's no bounds at all and that the blood river's size only fills the ones with the window size, therefore you have your character endlessly scoring as it already fell and is not intervened by the blood river)

I dunno either