Initial scaffolding.

scenes/effects/flash_effect.gd

@@ -0,0 +1,27 @@
+class_name FlashEffect
+extends BaseEffect
+
+@export var flash_color: Color = Color.WHITE
+@export var flash_speed: float = 10.0
+
+var _timer: float = 0.0
+var _original_material: Material
+
+func start(target: Node) -> void:
+    _timer = 0.0
+    if target is CanvasItem:
+        _original_material = target.material
+        # Apply a ShaderMaterial that handles the flash
+        var flash_material = ShaderMaterial.new()
+        flash_material.shader = preload("res://shaders/flash.gdshader")
+        target.material = flash_material
+
+func process(delta: float, target: Node) -> void:
+    _timer += delta
+    if target.material is ShaderMaterial:
+        var intensity = (sin(_timer * flash_speed) + 1.0) / 2.0
+        target.material.set_shader_parameter("flash_intensity", intensity)
+
+func stop(target: Node) -> void:
+    if target is CanvasItem:
+        target.material = _original_material