Arrange fleet abilities around fire stick

ui/AbilityButtonLayout.gd

@@ -0,0 +1,49 @@
+class_name AbilityButtonLayout
+extends Node
+
+# Keeps the aimed fleet abilities close to the firing thumb. One ability sits
+# directly above the fire stick; multiple abilities fan through its upper-left
+# quadrant instead of becoming a detached horizontal toolbar.
+
+@export var arc_radius: float = 280.0
+
+@onready var fire_stick: Control = get_node("../UI/FireStick")
+@onready var buttons: Array = [
+	get_node("../UI/DashButton"),
+	get_node("../UI/GasBombButton"),
+	get_node("../UI/LaserButton"),
+]
+
+var visibility_signature: int = -1
+
+
+func _ready() -> void:
+	get_viewport().size_changed.connect(_layout_visible_buttons)
+	_layout_visible_buttons.call_deferred()
+
+
+func _process(_delta: float) -> void:
+	var signature: int = 0
+	for i in range(buttons.size()):
+		if buttons[i].visible:
+			signature |= 1 << i
+	if signature == visibility_signature:
+		return
+	visibility_signature = signature
+	_layout_visible_buttons()
+
+
+func _layout_visible_buttons() -> void:
+	var visible_buttons: Array = buttons.filter(func(button): return button.visible)
+	if visible_buttons.is_empty():
+		return
+	var center: Vector2 = fire_stick.global_position + fire_stick.size * 0.5
+	for i in range(visible_buttons.size()):
+		# Screen coordinates grow downward: PI points left and 3*PI/2 points
+		# upward, tracing exactly the useful quarter around a bottom-right stick.
+		var weight: float = 1.0 if visible_buttons.size() == 1 \
+			else float(i) / float(visible_buttons.size() - 1)
+		var angle: float = lerpf(PI, PI * 1.5, weight)
+		var button: Control = visible_buttons[i]
+		button.global_position = center + Vector2.from_angle(angle) * arc_radius \
+			- button.size * 0.5