Great for a first game.
But it's a lot better than other beginners. I mean for one, it actually worked.
I think the only thing you would need to work on to make the game fun, is to actually put stuff in the game to do, I mean there was only one real obstacle. Maybe you could have made it so you had to get a key to open the door, instead of just clicking on some other ninja.
I think that animation wise, it looked nice. I really like that you did add a bunch of things to the landscape, like a bridge or the powerlines. And the grass, actually looked like grass, not just a big green rectangle. I think you could have added a bit more detail into some other stuff such as the big rock wall that you fall by, but it was okay.