1 files changed, 32 insertions, 0 deletions
diff --git a/src/LivingVillage.Desktop/TitleScreen.fs b/src/LivingVillage.Desktop/TitleScreen.fs
index 0dcd693..2e760ef 100644
--- a/src/LivingVillage.Desktop/TitleScreen.fs
+++ b/src/LivingVillage.Desktop/TitleScreen.fs
@@ -88,6 +88,38 @@ module TitleScreen =
         if frameCount >= 120L then 0.0f
         else 1.0f - float32 frameCount / 120.0f
 
+    // ---- P42 environment FX: all pure functions of the frame counter, so re-rendering
+    // the same frame is byte-identical. Shared by the splash and the start menu. ----
+
+    /// Sine ripple amplitude of the water band. Kept as a named constant so a test can
+    /// assert it never regresses below the full-frame visibility budget (>= 0.25).
+    let waterRippleAmplitude = 0.32f
+
+    /// Water ripple phase: moves with the frame and is dense across tile columns
+    /// (~5 tiles per wave), so adjacent 28px columns differ enough to read at 1x.
+    let waterRipplePhase (frame: int64) (column: int) (rowIndex: int) : float32 =
+        float32 (frame % 4096L) / 5.0f + float32 column * 1.25f + float32 rowIndex * 0.6f
+
+    /// Water ripple brightness per tile column: base 1.0 +/- waterRippleAmplitude sine.
+    let waterRippleBrightness (frame: int64) (column: int) (rowIndex: int) : float32 =
+        1.0f + waterRippleAmplitude * sin (waterRipplePhase frame column rowIndex)
+
+    /// Water crest lift in whole pixels (-2..2) for a tile column; drives the moving
+    /// ripple highlight without ever leaving a hole in the water band.
+    let waterRippleLift (frame: int64) (column: int) (rowIndex: int) : int =
+        int (System.Math.Round(float (sin (waterRipplePhase frame column rowIndex) * 2.0f), System.MidpointRounding.AwayFromZero))
+
+    /// True on columns sitting on a wave crest; the renderer caps these with a bright
+    /// highlight and the frame analysis counts them.
+    let waterRippleCrest (frame: int64) (column: int) (rowIndex: int) : bool =
+        sin (waterRipplePhase frame column rowIndex) > 0.55f
+
+    /// Eave-lantern breathing glow alpha, bounded to [40, 96]; phase moves with the
+    /// frame and the lantern index so the bank lanterns breathe out of step.
+    let lanternBreathAlpha (frame: int64) (index: int) : int =
+        let phase = float32 (frame % 4096L) / 22.0f + float32 index * 1.3f
+        68 + int (System.Math.Round(float (sin phase * 28.0f), System.MidpointRounding.AwayFromZero))
+
     let layout (viewportWidth: int) (viewportHeight: int) : TitleLayout =
         let width = max 320 viewportWidth
         let height = max 240 viewportHeight