GunSprint.cs

using UnityEngine;

public class GunSprint : MonoBehaviour {
    [SerializeField] private Bullet _bulletPrefab;
    [SerializeField] private Transform _spawnPoint;
    [SerializeField] private ParticleSystem _smokeSystem;
    [SerializeField] private LayerMask _targetLayer;

    [SerializeField] private float _bulletSpeed = 12;
    [SerializeField] private float _torque = 120;
    [SerializeField] private float _maxTorqueBonus = 150;

    [SerializeField] private float _maxAngularVelocity = 10;

    [SerializeField] private float _forceAmount = 600;
    [SerializeField] private float _maxUpAssist = 30;

    [SerializeField] private float _smokeLength = 0.5f;

    [SerializeField] private float _maxY = 10;
    
    private Rigidbody _rb;
    private float _lastFired;
    private bool _fire;
    
    private void Awake() => _rb = GetComponent<Rigidbody>();

    void Update() {
        // Clamp max velocity
        _rb.angularVelocity = new Vector3(0, 0, Mathf.Clamp(_rb.angularVelocity.z, -_maxAngularVelocity, _maxAngularVelocity));
        
        if (Input.GetMouseButtonDown(0)) {
            // Check if on target
            var hitsTarget = Physics.Raycast(_spawnPoint.position, _spawnPoint.forward, float.PositiveInfinity, _targetLayer);
            if (hitsTarget) GameManager.Instance.ToggleSlowMo(true);

            // Spawn
            var bullet = Instantiate(_bulletPrefab, _spawnPoint.position, _spawnPoint.rotation);
            bullet.Init(_spawnPoint.forward * _bulletSpeed, hitsTarget);
            _smokeSystem.Play();
            _lastFired = Time.time;

            // Apply force - More up assist depending on y position
            var assistPoint = Mathf.InverseLerp(0, _maxY, _rb.position.y);
            var assistAmount = Mathf.Lerp(_maxUpAssist, 0, assistPoint);
            var forceDir = -transform.forward * _forceAmount + Vector3.up * assistAmount;
            if (_rb.position.y > _maxY) forceDir.y = Mathf.Min(0, forceDir.y);
            _rb.AddForce(forceDir);

            // Determine the additional torque to apply when swapping direction
            var angularPoint = Mathf.InverseLerp(0, _maxAngularVelocity, Mathf.Abs(_rb.angularVelocity.z));
            var amount = Mathf.Lerp(0, _maxTorqueBonus, angularPoint);
            var torque = _torque + amount;
            
            // Apply torque
            var dir = Vector3.Dot(_spawnPoint.forward, Vector3.right) < 0 ? Vector3.back : Vector3.forward;
            _rb.AddTorque(dir * torque);
        }

        if (_smokeSystem.isPlaying && _lastFired + _smokeLength < Time.time) _smokeSystem.Stop();
    }
}



// Put this in its own file
public class Bullet : MonoBehaviour {
    [SerializeField] private GameObject _explosionPrefab;
    [SerializeField] private GameObject _trail;
    private Rigidbody _rb;
    private bool _hitsTarget;

    private void Awake() => _rb = GetComponent<Rigidbody>();

    public void Init(Vector3 vel, bool hitsTarget) {
        _rb.velocity = vel;
        _hitsTarget = hitsTarget;
        if (_hitsTarget) _trail.SetActive(true);
    }

    private void OnCollisionEnter(Collision collision) {
        Instantiate(_explosionPrefab, transform.position, Quaternion.identity);

        if (_hitsTarget) {
            GameManager.Instance.ToggleSlowMo(false);
        }

        Destroy(gameObject);
    }
}

I downloaded this to learn more about how this works, im new to unity so forgive me but what is GameManager? when i coped this code i get this error in visual studio "The name 'GameManager' does not exist in the current context [Assembly-CSharp]" How do i fix this? thanks

@MrUniTech just remove it. Game manager is a different script.