same script, different results every test run

Questions & Answers
1

Hi, I was trying to create a character controller and I had a problem where when I try to walk it’d neither go sonic speed or just not move at all. Yesterday I couldn’t even get it to move but this morning it moves way too fast.
Here’s the code (don’t mind the jumping part it’s bad and ill fix it later):
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Controller : MonoBehaviour
{
    private Rigidbody rigidbody;

    public float walkSpeed;
    public float jumpPower;

    void Awake()
    {
        rigidbody = gameObject.GetComponent<Rigidbody>();
    }

    // Update is called once per frame
    void Update()
    {

        float walkMovement = 0;
        float strafeMovement = 0;

        if (Input.GetKey(KeyCode.W))
        {
            walkMovement = walkSpeed;
        }
        if (Input.GetKey(KeyCode.S))
        {
            walkMovement = -walkSpeed;
        }
        // --------------------------------------------------------------------
        if (Input.GetKey(KeyCode.A))
        {
            strafeMovement = walkSpeed;
        }
        if (Input.GetKey(KeyCode.D))
        {
            strafeMovement = -walkSpeed;
        }
        // --------------------------------------------------------------------
        if (Input.GetKeyDown(KeyCode.Space))
        {
            rigidbody.AddForce(0, jumpPower, 0);
        }

        // Move character
        rigidbody.AddRelativeForce(Vector3.forward * walkMovement);
        rigidbody.AddRelativeForce(Vector3.left * strafeMovement);
    }
}
2

Replace Update() with FixedUpdate(). Your problem is related to the frames per second. But the more fps, the more often the force is applied and the higher the speed of the character. FixedUpdate() is called regardless of fps. Therefore, any device will always have the same speed.

Note: in your script, the player can speed up infinitely. To prevent this, enter the variable

public float maxSpeed = 10;

and write the following code at the end of the FixedUpdate() function:

var velocity = rigidbody.velocity;
velocity.y = 0;
velocity = Vector3.ClampMagnitude (velocity, maxSpeed);
velocity.y = rigidbody.velocity.y;
rigidbody.velocity = velocity;