urm03/scripts/grunt.gd

extends CharacterBody2D
## Enemy body — used by both greybox enemy types via scene exports:
## the untagged grunt (neutral hue, no tag behavior of its own) and
## the self-heating burster (self_heat_rate > 0: HEAT-tagged walking
## bomb, orange base per the one-color legibility floor — the literal
## tag mirror made playable: its own mechanic is your ammo if you
## knock it into the swarm before it pops).
##
## Heat: accumulates, glows, detonates at threshold (HEAT's signature).
## Detonation is symmetric — it damages enemies AND the mech in radius
## (one grammar on both sides; your heat play prices standing close).
## Detonation deals no knockback: moving things is KINETIC's verb.
##
## Chemistry row KINETIC+HEAT (*Spread*): a heated enemy slammed into
## another (knockback impact, not a walking bump) spreads its heat on
## contact, passes momentum, and fires the authorship-loud feedback
## stack via the arena. Struck enemies are heated AND shoved, so
## chains can cascade — chemistry feeding chemistry, decaying with
## each hop.

signal died

@export var speed := 70.0
@export var hp := 3.0
@export var contact_damage := 5.0
@export var contact_interval := 0.5
@export var knockback_decay := 5.0
@export var body_radius := 8.0
@export var base_color := Color(0.45, 0.47, 0.4)
@export var salvage_value := 1
## Placeholder sprite; overridden per scene (grunt vs burster).
@export var sprite_path := "res://assets/sprites_ph/grunt_ph.png"
## > 0 makes this a burster: heat/second it applies to itself.
@export var self_heat_rate := 0.0

@export_group("Heat status")
@export var heat_threshold := 3.0
@export var detonation_damage := 1.5
@export var detonation_mech_damage := 6.0
@export var detonation_radius := 56.0

@export_group("Chemistry KINETIC+HEAT")
## Minimum knockback speed for an impact to count as "knocked into".
@export var chem_min_knockback := 120.0
## Fraction of the striker's heat the struck enemy receives.
@export var chem_spread_factor := 1.0
## Fraction of the striker's knockback passed to the struck enemy.
@export var chem_momentum_factor := 0.45

const FX_RING := preload("res://scripts/fx_ring.gd")

var heat := 0.0
var _knockback := Vector2.ZERO
var _contact_cd := 0.0
var _chem_cd := 0.0
var _flash := 0.0
var _dead := false
var _mech: Node2D
var _sprite: Sprite2D


func _ready() -> void:
	add_to_group("enemies")
	if self_heat_rate > 0.0:
		add_to_group("bursters")
	_mech = get_tree().get_first_node_in_group("mech")
	_sprite = Sprite2D.new()
	_sprite.texture = load(sprite_path)
	add_child(_sprite)
	_update_tint()


func _physics_process(delta: float) -> void:
	if self_heat_rate > 0.0:
		heat += self_heat_rate * delta
		queue_redraw()
	if heat >= heat_threshold:
		_detonate()
		return

	_contact_cd -= delta
	_chem_cd -= delta
	var seek := Vector2.ZERO
	if is_instance_valid(_mech):
		seek = (_mech.global_position - global_position).normalized() * speed
	_knockback = _knockback.lerp(Vector2.ZERO, 1.0 - exp(-knockback_decay * delta))
	velocity = seek + _knockback
	move_and_slide()

	for i in get_slide_collision_count():
		var col := get_slide_collision(i)
		var collider := col.get_collider()
		if collider == _mech:
			if _contact_cd <= 0.0:
				_mech.take_damage(contact_damage)
				_contact_cd = contact_interval
		elif collider is CharacterBody2D and collider.is_in_group("enemies"):
			if heat > 0.0 and _chem_cd <= 0.0 and _knockback.length() >= chem_min_knockback:
				_chem_cd = 0.12
				collider.add_heat(heat * chem_spread_factor)
				collider.hit(0.0, _knockback * chem_momentum_factor)
				var arena := get_tree().get_first_node_in_group("arena")
				if arena != null:
					var axis: Vector2 = (collider.global_position - global_position).normalized()
					arena.chemistry_proc(col.get_position(), axis)

	if _flash > 0.0:
		_flash -= delta
		queue_redraw()
	_update_tint()


## The sprite carries the dynamic feedback the primitive used to: heat
## tints the body toward orange (HEAT's read), a hit flashes it bright.
## The heat-aura ring stays a _draw overlay (below the sprite).
func _update_tint() -> void:
	if _sprite == null:
		return
	if _flash > 0.0:
		_sprite.modulate = Color(2.5, 2.5, 2.5)
		return
	var heat_k := clampf(heat / heat_threshold, 0.0, 1.0)
	_sprite.modulate = Color(1, 1, 1).lerp(Color(1.5, 0.75, 0.4), heat_k)


func hit(damage: float, kb: Vector2) -> void:
	if _dead:
		return
	hp -= damage
	_knockback += kb
	_flash = 0.12
	_update_tint()
	queue_redraw()
	if hp <= 0.0:
		_die()


func add_heat(amount: float) -> void:
	if _dead:
		return
	heat += amount
	_update_tint()
	queue_redraw()


func _detonate() -> void:
	if _dead:
		return
	for e in get_tree().get_nodes_in_group("enemies"):
		if e == self:
			continue
		if global_position.distance_to(e.global_position) <= detonation_radius:
			e.hit(detonation_damage, Vector2.ZERO)
	if is_instance_valid(_mech) and global_position.distance_to(_mech.global_position) <= detonation_radius:
		_mech.take_damage(detonation_mech_damage)
	var ring: Node2D = FX_RING.new()
	ring.position = global_position
	ring.max_radius = detonation_radius
	get_parent().add_child(ring)
	_die()


func _die() -> void:
	if _dead:
		return
	_dead = true
	died.emit()
	queue_free()


func _draw() -> void:
	# Body is now the sprite; _draw carries only the heat-aura ring
	# (renders under the sprite, extends past it — a visible glow).
	var heat_k := clampf(heat / heat_threshold, 0.0, 1.0)
	if heat_k > 0.0:
		draw_arc(Vector2.ZERO, body_radius + 3.0, 0.0, TAU, 24, Color(0.95, 0.55, 0.2, 0.4 + heat_k * 0.5), 1.5)