Wow that's a really cool art style!
The only thing I didn't like was the upgrade options kind of achieving the same effect. It would have been cool to have upgrade options like slowing the slider down or additionally having to hit the perfect throwing angle which could give you a bit more control of the throw.
But that's really only my opinion and you could argue that the slider should stay as it is and rather have the player adapt to it's movement, so this is a really nice game overall!