Why does increasing y-velocity in my juggling simulation decrease x-velocity?

[Meowzers]

Hi, I am working with a juggling simulation to better my understanding of projectile motion. However, I encountered a slight problem.

To my understanding, an initial y velocity and an initial x velocity are independent of each other. A y-velocity affects the height of how high the ball travels in the air whereas the x-velocity affects the horizontal displacement of the ball (to the other hand of the juggler).

So, let's say I want the ball to be juggled higher, why does it seem to also affect the x-velocity (as I observed in the simulation) when it's supposed to be independent of the height (y-axis)? The higher inital y-velocity I input, the higher the ball goes. So why does the inital x-velocity need to decrease? Isn't it supposed to stay the same?

 

[SGT]

Velocity is a vector. In your case it is decomposed in x and y components. If the modulus of your vector is constant, increasing one component will decrease the other.