MonoBehaviour

using UnityEngine;

public class PlayerController : MonoBehaviour
{
  [SerializeField] private float speed = 5f;
  private Rigidbody _rb;
  private Vector3   _inputDir;

  void Awake()
  {
      // Cache component — no dependency on other scripts
      _rb = GetComponent<Rigidbody>();
  }

  void Start()
  {
      // Setup that needs GameManager.Awake to have finished
      GameManager.Instance.RegisterPlayer(this);
  }

  void Update()
  {
      // Read input every frame
      float h = Input.GetAxisRaw("Horizontal");
      float v = Input.GetAxisRaw("Vertical");
      _inputDir = new Vector3(h, 0, v).normalized;
  }

  void FixedUpdate()
  {
      // Physics move — do not use Time.deltaTime here
      _rb.MovePosition(_rb.position + _inputDir * speed * Time.fixedDeltaTime);
  }

  void OnDestroy()
  {
      GameManager.Instance.UnregisterPlayer(this);
  }
}

using UnityEngine;
using System;

// Full lifecycle component — pairs well with an event system
public class HealthComponent : MonoBehaviour
{
  [SerializeField] private int maxHp = 100;
  private int _currentHp;

  public event Action<int,int> OnHealthChanged;  // (current, max)
  public event Action           OnDied;

  void Awake() => _currentHp = maxHp;

  void OnEnable()
  {
      // Subscribe when the component becomes active
      GameEvents.OnDamageDealt += TakeDamage;
  }

  void OnDisable()
  {
      // Unsubscribe immediately — avoid calls while disabled
      GameEvents.OnDamageDealt -= TakeDamage;
  }

  public void TakeDamage(int amount)
  {
      _currentHp = Mathf.Max(0, _currentHp - amount);
      OnHealthChanged?.Invoke(_currentHp, maxHp);
      if (_currentHp == 0) OnDied?.Invoke();
  }
}