Basically, Haoshoku Haki is where a large circle part appears on my character after pressing a certain key. Anyone that gets caught in that circle part is unable to move at all for a few seconds.
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Create an animation for the circle thing, then you’d mention if the character presses whatever the keybind is then the animation would play.
If a players position is within that circle, their humanoid walk speed would be set to 0.
Loop through all players, check the magnitude of each player to you (Magnitude is the radius of the sphere). If they are inside the sphere (magnitude <= sphere’s radius), do things you want people to be while inside the sphere.