TableFlipper.cs

using UnityEngine;
using UnityEngine.Events;

public class TableFlipper : MonoBehaviour {

    [SerializeField]
    float _power;

    [SerializeField]
    float _powerUpSpeed = 1;

    [SerializeField]
    float _forceMultiplier;

    [SerializeField]
    Vector3 _forcePoint = Vector3.back;

    [SerializeField]
    Vector3 _forceDirection = Vector3.up;

    [Header("Timer"), SerializeField]
    bool _timerEnabled;

    [SerializeField]
    float _timeBeforeForce = 2;

    [SerializeField]
    float _forceTimer;

    public PowerEvent OnPowerChanged;

    #region Properties
    public Vector3 ForceDirection {
        get { return _forceDirection; }
        set { _forceDirection = value; }
    }

    public float ForceMultiplier {
        get { return _forceMultiplier; }
        set { _forceMultiplier = value; }
    }

    public Vector3 ForcePoint {
        get { return _forcePoint; }
        set { _forcePoint = value; }
    }

    public float ForceTimer {
        get { return _forceTimer; }
        set { _forceTimer = value; }
    }

    public float Power {
        get { return _power; }
        set {
            float newValue = Mathf.Clamp01(value);

            if(newValue == Power) return;

            _power = newValue;

            if(OnPowerChanged != null) OnPowerChanged.Invoke(Power);
        }
    }

    public float PowerUpSpeed {
        get { return _powerUpSpeed; }
        set { _powerUpSpeed = value; }
    }

    Rigidbody RigidbodyComponent { get; set; }

    public float TimeBeforeForce {
        get { return _timeBeforeForce; }
        set { _timeBeforeForce = value; }
    }

    public bool TimerEnabled {
        get { return _timerEnabled; }
        set { _timerEnabled = value; }
    }
    #endregion

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

    void Update() {
        UpdateInput();
        UpdateTimer();
    }

    void UpdateInput() {
        if(Input.GetKeyDown(KeyCode.Space)) {
            if(RigidbodyComponent.IsSleeping()) {
                StartTimer();
                Power += PowerUpSpeed * Time.deltaTime;
            }
        }
    }

    void UpdateTimer() {
        if(TimerEnabled) {
            if(ForceTimer > 0) {
                ForceTimer = Mathf.Max(ForceTimer - Time.deltaTime, 0);

                if(ForceTimer == 0) {
                    TimerEnabled = false;
                    ApplyForce();
                }
            }
        }
    }

    [ContextMenu("Apply Force")]
    public void ApplyForce() {
        RigidbodyComponent.AddForceAtPosition(ForceDirection * ForceMultiplier * Power, transform.TransformPoint(ForcePoint), ForceMode.VelocityChange);
    }

    [ContextMenu("Start Timer")]
    public void StartTimer() {
        if(!TimerEnabled && RigidbodyComponent.IsSleeping()) {
            ForceTimer = TimeBeforeForce;
            TimerEnabled = true;
            Power = 0;
        }
    }

    void OnDrawGizmos() {
        Gizmos.color = Color.blue;
        Gizmos.DrawSphere(transform.TransformPoint(ForcePoint), .125f);
    }

    [System.Serializable]
    public class PowerEvent : UnityEvent<float> { }
}