Input and player control

In plain English

The Input System is Unity's newer input package, while the legacy Input Manager is the older built-in approach that still works through methods like GetAxis. Reading axes returns a value from -1 to 1, such as left and right on the horizontal axis. Update runs every rendered frame and is the place to read input, while FixedUpdate runs at a steady physics step and is the place to apply forces to a Rigidbody. A Rigidbody is the component that lets physics move an object, so change its position with physics methods rather than the Transform.

Step by step

1. 1Create a GameObject with a Rigidbody and a collider.
2. 2Add a PlayerController component to the same object.
3. 3Read the horizontal and vertical axes.
4. 4Build a direction vector and normalise it.
5. 5Move the Rigidbody with MovePosition in FixedUpdate.

using UnityEngine;

public class PlayerController : MonoBehaviour
{
    [SerializeField] private float speed = 6f;
    private Rigidbody body;

    private void Awake()
    {
        body = GetComponent<Rigidbody>();
    }

    private void FixedUpdate()
    {
        float horizontal = Input.GetAxisRaw("Horizontal");
        float vertical = Input.GetAxisRaw("Vertical");
        Vector3 direction = new Vector3(horizontal, 0f, vertical).normalized;
        body.MovePosition(body.position + direction * speed * Time.fixedDeltaTime);
    }
}

Common mistakes

• Reading input inside FixedUpdate misses rapid presses, because physics runs at a fixed step rather than every frame.
• Moving a Rigidbody by setting its Transform position bypasses physics and can cause tunnelling or jitter.
• Forgetting to add a Rigidbody means GetComponent returns null and the script throws at runtime.
• Skipping the normalise step makes diagonal movement faster than straight movement.