Added effects manager and two effects to test attached to the player

scene.

scripts/effects/blinker_effect.gd

@@ -0,0 +1,90 @@
+class_name BlinkerEffect
+extends BaseEffect
+
+## How many blink cycles per second.
+@export_range(0.0, 60.0) var blink_frequency: float = 8.0
+
+## Fraction of each cycle the sprite is visible (0.0–1.0).
+@export_range(0.0, 1.0) var blink_length: float = 0.5
+
+## Minimum alpha when "off" (0.0 = fully invisible, 1.0 = fully visible).
+@export_range(0.0, 1.0) var min_alpha: float = 0.0
+
+## Maximum alpha when "on" (0.0–1.0).
+@export_range(0.0, 1.0) var max_alpha: float = 1.0
+
+## Duration of the fade-in at the start of the effect (seconds).
+@export_range(0.0, 5.0) var start_ease: float = 0.0
+
+## Easing curve for the fade-in.
+@export_enum("Linear", "Smooth", "Ease-In", "Ease-Out", "Ease-In-Out") var start_ease_mode: int = 1
+
+## Duration of the fade-out at the end of the effect (seconds).
+@export_range(0.0, 5.0) var end_ease: float = 0.0
+
+## Easing curve for the fade-out.
+@export_enum("Linear", "Smooth", "Ease-In", "Ease-Out", "Ease-In-Out") var end_ease_mode: int = 1
+
+var _original_modulate: Color
+
+
+func start(target: Node) -> void:
+    super.start(target)
+    if target is CanvasItem:
+        _original_modulate = target.modulate
+
+
+func process(delta: float, target: Node) -> void:
+    super.process(delta, target)
+    if target is CanvasItem:
+        var alpha: float = _compute_alpha(_elapsed)
+        target.modulate = Color(_original_modulate.r, _original_modulate.g, _original_modulate.b, alpha)
+
+
+func stop(target: Node) -> void:
+    if target is CanvasItem:
+        target.modulate = _original_modulate
+
+
+## Compute the combined eased alpha for a given elapsed time.
+func _compute_alpha(elapsed: float) -> float:
+    if duration <= 0.0:
+        return 1.0
+
+    var t: float = min(elapsed, duration)
+
+    # Blink pulse: on/off cycling at the given frequency and duty cycle
+    var period := 1.0 / blink_frequency if blink_frequency > 0.0 else 1.0
+    var phase := fmod(t, period) / period
+
+    var pulse: float = min_alpha
+    if phase < blink_length:
+        var pulse_progress = phase / blink_length if blink_length > 0.0 else 1.0
+        if pulse_progress < 0.5:
+            pulse = min_alpha + (max_alpha - min_alpha) * _ease_value(pulse_progress * 2.0, 2)
+        else:
+            pulse = min_alpha + (max_alpha - min_alpha) * _ease_value((1.0 - pulse_progress) * 2.0, 3)
+
+    # Start ease: fade from fully visible into the blink pattern
+    if t < start_ease and start_ease > 0.0:
+        var fade_in = _ease_value(t / start_ease, start_ease_mode)
+        return lerp(max_alpha, pulse, fade_in)
+
+    # End ease: fade from blink pattern back to fully visible
+    if t > duration - end_ease and end_ease > 0.0:
+        var fade_progress = (t - (duration - end_ease)) / end_ease
+        var fade_out = _ease_value(fade_progress, end_ease_mode)
+        return lerp(pulse, max_alpha, fade_out)
+
+    return pulse
+
+
+## Apply easing to a 0.0–1.0 normalized value based on the selected mode.
+func _ease_value(value: float, mode: int) -> float:
+    match mode:
+        0: return value  # Linear
+        1: return smoothstep(0.0, 1.0, value)  # Smooth
+        2: return ease(value, -2.0)  # Ease-In (accelerating)
+        3: return ease(value, 2.0)  # Ease-Out (decelerating)
+        4: return ease(value, 3.0)  # Ease-In-Out (S-curve)
+    return value