Expand and stage boss encounter

boss/BossMinion.gd

@@ -9,9 +9,16 @@ const COMBAT_TARGET = preload("res://core/CombatTarget.gd")
 @export var max_hp: int = 5
 @export var speed: float = 245.0
 @export var acceleration: float = 520.0
+@export var expulsion_speed: float = 520.0
+@export var dash_speed: float = 760.0
 
 var boss: Node2D
 const REDRAW_INTERVAL: float = 1.0 / 12.0
+const EXPULSION_SECONDS: float = 0.85
+const BRAKE_SECONDS: float = 0.42
+const DASH_SECONDS: float = 0.48
+
+enum Motion { EXPELLED, CHASING, BRAKING, DASHING }
 
 var hp: int = 5
 var velocity: Vector2 = Vector2.ZERO
@@ -19,6 +26,11 @@ var phase: float = 0.0
 var dead: bool = false
 var redraw_left: float = 0.0
 var fleet: Node2D = null
+var motion: int = Motion.CHASING
+var motion_left: float = 0.0
+var dash_cooldown: float = 0.0
+var dash_direction: Vector2 = Vector2.ZERO
+var uses_dash_pattern: bool = false
 
 
 func _ready() -> void:
@@ -31,25 +43,71 @@ func _ready() -> void:
 	queue_redraw()
 
 
+# The boss throws hatchlings clear of its now much larger silhouette before
+# they acquire the fleet. Every third hatchling also gets the stop-and-lunge
+# rhythm requested in #189; the others remain steady pursuers so a wave is
+# varied rather than uniformly twitchy.
+func expel(direction: Vector2, dashes: bool) -> void:
+	var outward: Vector2 = direction.normalized()
+	uses_dash_pattern = dashes
+	motion = Motion.EXPELLED
+	motion_left = EXPULSION_SECONDS * randf_range(0.8, 1.2)
+	velocity = outward * expulsion_speed * randf_range(0.85, 1.15)
+	dash_cooldown = randf_range(1.2, 2.8)
+
+
 func _physics_process(delta: float) -> void:
 	phase += delta
 	if not is_instance_valid(fleet):
 		fleet = get_tree().get_first_node_in_group("player_fleet")
-	if fleet != null and not fleet.ships.is_empty():
-		var to_fleet: Vector2 = fleet.get_centroid() - global_position
-		if to_fleet.length() > 1.0:
-			velocity = velocity.move_toward(to_fleet.normalized() * speed,
-				acceleration * delta)
-			global_position += velocity * delta
-			if velocity.length() > 4.0:
-				rotation = lerp_angle(rotation, velocity.angle() + PI / 2.0,
-					7.0 * delta)
+	_update_motion(delta)
+	global_position += velocity * delta
+	if velocity.length() > 4.0:
+		rotation = lerp_angle(rotation, velocity.angle() + PI / 2.0,
+			7.0 * delta)
 	redraw_left -= delta
 	if redraw_left <= 0.0:
 		redraw_left = REDRAW_INTERVAL
 		queue_redraw()
 
 
+func _update_motion(delta: float) -> void:
+	if motion == Motion.EXPELLED:
+		motion_left -= delta
+		if motion_left <= 0.0:
+			motion = Motion.CHASING
+		return
+	if fleet == null or fleet.ships.is_empty():
+		velocity = velocity.move_toward(Vector2.ZERO, acceleration * delta)
+		return
+	var to_fleet: Vector2 = fleet.get_centroid() - global_position
+	if motion == Motion.BRAKING:
+		motion_left -= delta
+		velocity = velocity.move_toward(Vector2.ZERO, acceleration * 2.2 * delta)
+		if motion_left <= 0.0:
+			motion = Motion.DASHING
+			motion_left = DASH_SECONDS
+			dash_direction = to_fleet.normalized().rotated(randf_range(-0.42, 0.42))
+		return
+	if motion == Motion.DASHING:
+		motion_left -= delta
+		velocity = velocity.move_toward(dash_direction * dash_speed,
+			acceleration * 4.0 * delta)
+		if motion_left <= 0.0:
+			motion = Motion.CHASING
+			dash_cooldown = randf_range(1.8, 3.8)
+		return
+	if uses_dash_pattern:
+		dash_cooldown -= delta
+		if dash_cooldown <= 0.0:
+			motion = Motion.BRAKING
+			motion_left = BRAKE_SECONDS
+			return
+	if to_fleet.length() > 1.0:
+		velocity = velocity.move_toward(to_fleet.normalized() * speed,
+			acceleration * delta)
+
+
 func take_damage(amount: int) -> bool:
 	if dead:
 		return false