game: add xp orbs

scenes/xp_orb.gd

@@ -2,3 +2,24 @@ class_name XPOrb
 extends Node2D
 
 @export var value: float
+@export var max_speed: float = 100.0
+@export var min_speed: float = 10.0
+
+var player: Player
+
+func _ready() -> void:
+	player = get_tree().get_first_node_in_group(GlobalConst.GROUP_PLAYER)
+
+func _physics_process(delta: float) -> void:
+	if not player:
+		return
+	
+	var to_player = player.global_position - global_position
+	var dist = to_player.length()
+	var attract_radius = player.player_stats.get_final("pickup_radius", player.modifiers)
+	if dist < 4:
+		return
+	if dist < attract_radius:
+		var dir = to_player.normalized()
+		var speed = lerp(min_speed, max_speed, (attract_radius - dist) / attract_radius)
+		global_position += dir * speed * delta