fix: improved spring behavior

src/Platforms/Spring/SpringPhysics.gd

@@ -12,14 +12,19 @@ var y_velocity = 0
 var friction = 0.91
 # TODO Only store velocity coming to the springs orientation
 var stored_incoming_velocity = 0
-var coupled_body = null
+var coupled_body_ref = weakref(null)
 var shock_ready = true
+var spring_sound_armed = false
 
 
 func _ready() -> void:
 	start_y = self.position.y
 
 
+func coupled_body():
+	return coupled_body_ref.get_ref()
+
+
 # TODO Limit spring deformation
 
 
@@ -31,16 +36,14 @@ func _physics_process(delta: float) -> void:
 		_Kinematic_Body_on_Spring()
 
 	var spring_force = spring_k * (self.start_y - self.position.y)
-	if coupled_body != null:
-		coupled_mass = mass + coupled_body.mass
+	if coupled_body() != null:
+		coupled_mass = mass + coupled_body().mass
 	else:
 		coupled_mass = mass
 
 	var weight_force = coupled_mass * PhysicsConst.gravity
 	var result_force = weight_force + spring_force
-	y_velocity = PhysicsFunc.two_step_euler(
-		y_velocity, result_force, coupled_mass, delta
-	)
+	y_velocity = PhysicsFunc.two_step_euler(y_velocity, result_force, coupled_mass, delta)
 
 	y_velocity *= friction
 
@@ -50,20 +53,21 @@ func _physics_process(delta: float) -> void:
 func _body_contact() -> bool:
 	var areas: Array = $SpringSkin.get_overlapping_areas()
 	for i in range(0, areas.size()):
-		coupled_body = areas[i].get_parent()
+		if !areas[i].get_parent().is_class("PhysicsBody2D"):
+			continue
+		if !areas[i].get_parent().is_on_floor():
+			return false
+		coupled_body_ref = weakref(areas[i].get_parent())
 		return true
-	coupled_body = null
 	return false
 
 
 func _Kinematic_Body_on_Spring() -> void:
 	var a_velocity = stored_incoming_velocity
-	var a_mass = coupled_body.mass
+	var a_mass = coupled_body().mass
 	var b_velocity = y_velocity
 	var b_mass = mass
-	y_velocity += PhysicsFunc.complete_unelastic_shock(
-		a_velocity, b_velocity, a_mass, b_mass
-	)
+	y_velocity += PhysicsFunc.complete_unelastic_shock(a_velocity, b_velocity, a_mass, b_mass)
 	stored_incoming_velocity = 0
 	shock_ready = false
 
@@ -75,19 +79,22 @@ func _on_SpringSkin_area_exited(_area: Area2D) -> void:
 	var transferred_kinetic_energy = potential_spring_energy * mass_ratio
 	var kinetic_energy_in_velocity = (
 		-sign(displacement)
-		* sqrt(
-				2 * transferred_kinetic_energy / max(coupled_mass - mass, 0.001)
-		)
+		* sqrt(2 * transferred_kinetic_energy / max(coupled_mass - mass, 0.001))
 	)
-	if coupled_body != null:
-		coupled_body.velocity.y += kinetic_energy_in_velocity
+	if coupled_body() != null:
+		coupled_body().velocity.y += kinetic_energy_in_velocity
+		coupled_body_ref = weakref(null)
+		spring_sound_armed = true
 
 
 func _on_EnteringVelocityDetector_area_entered(area: Area2D) -> void:
-		if area.get_parent().velocity.y > 0:
-			stored_incoming_velocity = area.get_parent().velocity.y
+	if !area.get_parent().is_class("PhysicsBody2D"):
+		return
+	if area.get_parent().velocity.y > 0:
+		stored_incoming_velocity = area.get_parent().velocity.y
 
 
 func _on_EnteringVelocityDetector_area_exited(area: Area2D) -> void:
-	if coupled_body == null:
-			$SpringSound.play()
+	if area.get_parent().is_class("PhysicsBody2D") && spring_sound_armed:
+		$SpringSound.play()
+		spring_sound_armed = false