feat: add post-processing pass and video settings menu

Enable glow/bloom, color adjustments, and MSAA+FXAA across all three
arenas so emissive ship/station accents actually bleed light and edges
read cleanly. Expose the player-facing knobs (anti-aliasing mode, glow
intensity, brightness) through a new Settings screen off the main menu,
persisted via a VideoSettings autoload that scales each arena's own
tuned Environment values on load rather than overwriting them.

Game/scripts/arena.gd

@@ -8,6 +8,9 @@ extends Node3D
 
 func _ready():
 	add_to_group("arena")
+	var world_env := get_node_or_null("WorldEnvironment") as WorldEnvironment
+	if world_env and world_env.environment:
+		VideoSettings.apply_to_environment(world_env.environment)
 
 
 func get_ball_spawn() -> Transform3D:

Game/scripts/main_menu.gd

@@ -129,6 +129,10 @@ func _on_match_pressed() -> void:
 	get_tree().change_scene_to_file("res://scenes/match.tscn")
 
 
+func _on_settings_pressed() -> void:
+	get_tree().change_scene_to_file("res://scenes/settings.tscn")
+
+
 func _on_spectate_pressed() -> void:
 	GameSettings.spectate_bot_a_path = _selected_path(bot_a_dropdown)
 	GameSettings.spectate_bot_b_path = _selected_path(bot_b_dropdown)

Game/scripts/settings_menu.gd

@@ -0,0 +1,70 @@
+extends Control
+
+# Settings screen: a small set of player-facing video knobs on top of
+# VideoSettings (the autoload holding + persisting them). Anti-aliasing
+# applies immediately since it's a Viewport-wide setting; glow/brightness
+# apply the next time an arena loads (see arena.gd), since they scale each
+# arena's own tuned Environment values rather than something viewport-wide.
+
+const MAIN_MENU_SCENE_PATH := "res://scenes/main_menu.tscn"
+
+const AA_OPTIONS := [
+	{"name": "Off", "mode": VideoSettings.AAMode.OFF},
+	{"name": "FXAA", "mode": VideoSettings.AAMode.FXAA},
+	{"name": "MSAA 4x", "mode": VideoSettings.AAMode.MSAA},
+	{"name": "MSAA 4x + FXAA", "mode": VideoSettings.AAMode.MSAA_FXAA},
+]
+
+@onready var aa_dropdown: OptionButton = %AADropdown
+@onready var glow_slider: HSlider = %GlowSlider
+@onready var glow_value_label: Label = %GlowValueLabel
+@onready var brightness_slider: HSlider = %BrightnessSlider
+@onready var brightness_value_label: Label = %BrightnessValueLabel
+
+
+func _ready() -> void:
+	aa_dropdown.clear()
+	var selected := 0
+	for i in AA_OPTIONS.size():
+		aa_dropdown.add_item(AA_OPTIONS[i]["name"])
+		if AA_OPTIONS[i]["mode"] == VideoSettings.aa_mode:
+			selected = i
+	aa_dropdown.select(selected)
+
+	glow_slider.value = VideoSettings.glow_scale
+	brightness_slider.value = VideoSettings.brightness
+	_update_glow_label()
+	_update_brightness_label()
+
+
+func _update_glow_label() -> void:
+	glow_value_label.text = "%d%%" % roundi(glow_slider.value * 100.0)
+
+
+func _update_brightness_label() -> void:
+	brightness_value_label.text = "%d%%" % roundi(brightness_slider.value * 100.0)
+
+
+func _on_aa_dropdown_item_selected(index: int) -> void:
+	VideoSettings.aa_mode = AA_OPTIONS[index]["mode"]
+	VideoSettings.apply_aa()
+
+
+func _on_glow_slider_value_changed(value: float) -> void:
+	VideoSettings.glow_scale = value
+	_update_glow_label()
+
+
+func _on_brightness_slider_value_changed(value: float) -> void:
+	VideoSettings.brightness = value
+	_update_brightness_label()
+
+
+func _on_back_pressed() -> void:
+	VideoSettings.save()
+	get_tree().change_scene_to_file(MAIN_MENU_SCENE_PATH)
+
+
+func _unhandled_input(event: InputEvent) -> void:
+	if event.is_action_pressed("ui_cancel"):
+		_on_back_pressed()

Game/scripts/video_settings.gd

@@ -0,0 +1,65 @@
+extends Node
+
+# Autoload: persisted player-facing video preferences (AA, glow, brightness).
+# AA is a Viewport-wide setting applied immediately via apply_aa(). Glow and
+# brightness instead scale each arena's own tuned Environment values (see
+# arena.gd's _ready(), which calls apply_to_environment() once per arena
+# load) rather than overwriting them outright, so the per-arena bloom tuning
+# in arena_01/02/03.tscn survives underneath the user's preference.
+
+enum AAMode { OFF, FXAA, MSAA, MSAA_FXAA }
+
+const SETTINGS_PATH := "user://settings.cfg"
+
+var aa_mode: AAMode = AAMode.MSAA_FXAA
+var glow_scale: float = 1.0
+var brightness: float = 1.0
+
+
+func _ready() -> void:
+	_load()
+	apply_aa()
+
+
+func _load() -> void:
+	var cfg := ConfigFile.new()
+	if cfg.load(SETTINGS_PATH) != OK:
+		return
+	aa_mode = cfg.get_value("video", "aa_mode", aa_mode) as AAMode
+	glow_scale = cfg.get_value("video", "glow_scale", glow_scale)
+	brightness = cfg.get_value("video", "brightness", brightness)
+
+
+func save() -> void:
+	var cfg := ConfigFile.new()
+	cfg.set_value("video", "aa_mode", aa_mode)
+	cfg.set_value("video", "glow_scale", glow_scale)
+	cfg.set_value("video", "brightness", brightness)
+	cfg.save(SETTINGS_PATH)
+
+
+func apply_aa() -> void:
+	var viewport := get_tree().root
+	match aa_mode:
+		AAMode.OFF:
+			viewport.msaa_3d = Viewport.MSAA_DISABLED
+			viewport.screen_space_aa = Viewport.SCREEN_SPACE_AA_DISABLED
+		AAMode.FXAA:
+			viewport.msaa_3d = Viewport.MSAA_DISABLED
+			viewport.screen_space_aa = Viewport.SCREEN_SPACE_AA_FXAA
+		AAMode.MSAA:
+			viewport.msaa_3d = Viewport.MSAA_4X
+			viewport.screen_space_aa = Viewport.SCREEN_SPACE_AA_DISABLED
+		AAMode.MSAA_FXAA:
+			viewport.msaa_3d = Viewport.MSAA_4X
+			viewport.screen_space_aa = Viewport.SCREEN_SPACE_AA_FXAA
+
+
+# Called once by each arena's _ready() to fold the user's glow/brightness
+# preference into that arena's own baked Environment tuning.
+func apply_to_environment(env: Environment) -> void:
+	if env == null:
+		return
+	env.glow_enabled = glow_scale > 0.0
+	env.glow_intensity *= glow_scale
+	env.adjustment_brightness *= brightness