spaceship/enemies/ArtilleryShell.gd

class_name ArtilleryShell
extends Node2D

# Self-contained travel -> explode sequence for the artillery enemy's attack
# (see EnemyArtilleryComponent). Lives independently of the
# enemy that fired it once launched - added to the tree root, exactly like
# EnemyProjectile/Projectile - so the shooter dying mid-flight doesn't
# cancel a shell already in the air.
#
# Shield interaction: a shield charge absorbs this hit entirely, same
# all-or-nothing semantics as every other damage source in this game
# (VesselShieldComponent.absorb_hit) - _explode() just calls
# Ship.take_damage() like everything else and lets that logic decide.

signal finished

# The tower fires as soon as it decides to; the warning is the shell you can
# SEE coming and the cross marking where it will land. There used to be a
# 1.8s charge-up before anything left the barrel, which arrived long before
# the threat was legible and mostly read as the tower being stuck.
@export var shell_speed: float = 460.0
@export var aoe_radius: float = 220.0
@export var damage: int = 3
@export var color: Color = Color(1.0, 0.5, 0.2)

enum Phase { TRAVELING, EXPLODING }

const EXPLOSION_DURATION: float = 0.8
# The impact cross. Small on purpose: it says WHERE, and the shell in flight
# already says that something is coming. A full blast-radius ring here read
# as an attack that had already happened.
const IMPACT_CROSS_RADIUS: float = 20.0
# #114: the blast throws real debris now. The ring alone read as a decal
# being stamped on the map; a burst gives the moment some weight, and it is
# the same LightBurstVFX every other explosion in the game is built from.
const BLAST_VFX = preload("res://vfx/BombBlastVFX.gd")
# Fins on the falling bomb, so it reads as an object with a direction rather
# than a travelling dot.
const FIN_LENGTH: float = 13.0

var phase: int = Phase.TRAVELING
var target: Vector2 = Vector2.ZERO
var shell_pos: Vector2 = Vector2.ZERO
var explosion_time: float = 0.0
var trail: PackedVector2Array = PackedVector2Array()


func _ready() -> void:
	add_to_group("artillery_shells")


func launch(from: Vector2, at: Vector2) -> void:
	target = at
	shell_pos = from
	phase = Phase.TRAVELING
	trail = PackedVector2Array([shell_pos])
	position = shell_pos
	queue_redraw()


func _process(delta: float) -> void:
	match phase:
		Phase.TRAVELING:
			var to_target: Vector2 = target - shell_pos
			var step: float = shell_speed * delta
			if to_target.length() <= step:
				shell_pos = target
				_explode()
			else:
				shell_pos += to_target.normalized() * step
				trail.append(shell_pos)
				while trail.size() > 14:
					trail.remove_at(0)
			position = shell_pos
			queue_redraw()
		Phase.EXPLODING:
			explosion_time -= delta
			queue_redraw()
			if explosion_time <= 0.0:
				finished.emit()
				queue_free()


func _explode() -> void:
	phase = Phase.EXPLODING
	explosion_time = EXPLOSION_DURATION
	position = target
	BLAST_VFX.spawn(get_tree().root, target, color)
	for ship in get_tree().get_nodes_in_group("player_ships"):
		if is_instance_valid(ship) and ship.global_position.distance_to(target) <= aoe_radius:
			ship.take_damage(damage)
	# #101: a bomb does not care whether what it landed on flies. The hitbox
	# is a child Area2D of the Building, which is a plain Node2D and would
	# otherwise be unhittable.
	for hitbox in get_tree().get_nodes_in_group("player_buildings"):
		if is_instance_valid(hitbox) and hitbox.global_position.distance_to(target) <= aoe_radius:
			hitbox.take_damage(damage)


func _draw() -> void:
	match phase:
		Phase.TRAVELING:
			# Where it will land, drawn on the ground. Local coordinates,
			# because this node rides along with the shell while it flies.
			_draw_impact_cross(target - shell_pos)
			for i in range(1, trail.size()):
				var alpha: float = float(i) / trail.size()
				draw_line(trail[i - 1] - shell_pos, trail[i] - shell_pos,
					Color(color, alpha * 0.6), 5.0, true)
				# A hot core down the middle of the smoke, brightest at the
				# bomb itself.
				draw_line(trail[i - 1] - shell_pos, trail[i] - shell_pos,
					Color(1.0, 0.94, 0.86, alpha * 0.5), 1.6, true)
			draw_circle(Vector2.ZERO, 14.0, Color(color, 0.35))
			# Fins, laid across the direction of travel.
			var heading: Vector2 = (target - shell_pos)
			heading = heading.normalized() if heading.length() > 0.001 else Vector2.DOWN
			var across: Vector2 = Vector2(-heading.y, heading.x) * FIN_LENGTH * 0.55
			var tail: Vector2 = -heading * FIN_LENGTH
			NeonDraw.draw_glowing_line(self, tail - across, tail + across, color, 0.9, 0.4)
			NeonDraw.draw_glowing_line(self, tail, heading * 6.0, color, 0.9, 0.45)
			NeonDraw.draw_glowing_circle(self, Vector2.ZERO, 8.0, color, 1.0)
		Phase.EXPLODING:
			var eprogress: float = 1.0 - explosion_time / EXPLOSION_DURATION
			var eradius: float = lerpf(30.0, aoe_radius, minf(eprogress * 1.5, 1.0))
			draw_circle(Vector2.ZERO, eradius, Color(color, (1.0 - eprogress) * 0.18))
			_draw_ring(eradius, 1.0 - eprogress)
			# A second ring chasing the first outwards, and a white flash
			# that is gone almost at once - the two together are what make a
			# blast read as a shock rather than a circle growing.
			if eprogress < 0.55:
				_draw_ring(eradius * 0.62, (0.55 - eprogress) * 1.6)
			if eprogress < 0.18:
				draw_circle(Vector2.ZERO, eradius * 0.7,
					Color(1.0, 0.95, 0.88, (0.18 - eprogress) * 3.0))


# A small cross where the shell will land, plus a dot at the exact point.
# Deliberately not a filled circle the size of the blast: the player needs to
# read "move off this spot" at a glance, and a large translucent area was
# easy to mistake for the explosion itself.
func _draw_impact_cross(at: Vector2) -> void:
	var r: float = IMPACT_CROSS_RADIUS
	for offset in [Vector2(r, r), Vector2(r, -r)]:
		draw_line(at - offset, at + offset, Color(color, 0.35), 7.0, true)
		draw_line(at - offset, at + offset, Color(1.0, 0.92, 0.86, 0.85), 2.5, true)
	draw_arc(at, r * 0.32, 0.0, TAU, 20, Color(color, 0.9), 2.5, true)


func _draw_ring(radius: float, alpha: float) -> void:
	draw_arc(Vector2.ZERO, radius, 0.0, TAU, 64, Color(color, 0.16 * alpha), 16.0, true)
	draw_arc(Vector2.ZERO, radius, 0.0, TAU, 64, Color(color, 0.5 * alpha), 6.0, true)
	draw_arc(Vector2.ZERO, radius, 0.0, TAU, 64, Color(1.0, 0.92, 0.86, 0.9 * alpha), 2.0, true)