diff --git a/src/ui/CSimpleFrame.cpp b/src/ui/CSimpleFrame.cpp
index 63fa796..b02a14c 100644
--- a/src/ui/CSimpleFrame.cpp
+++ b/src/ui/CSimpleFrame.cpp
@@ -1331,7 +1331,12 @@ void CSimpleFrame::SetBeingScrolled(int32_t a2, int32_t a3) {
 }
 
 void CSimpleFrame::SetFrameAlpha(uint8_t alpha) {
-    // TODO
+    if (this->m_alpha == alpha) {
+        return;
+    }
+
+    this->m_alpha = alpha;
+    this->UpdateAlpha();
 }
 
 void CSimpleFrame::SetFrameFlag(int32_t flag, int32_t on) {
@@ -1588,3 +1593,16 @@ void CSimpleFrame::UnregisterRegion(CSimpleRegion* region) {
 
     this->m_regions.UnlinkNode(region);
 }
+
+void CSimpleFrame::UpdateAlpha() {
+    for (auto region = this->m_regions.Head(); region; region = this->m_regions.Link(region)->Next()) {
+        region->OnColorChanged(false);
+    }
+
+    auto effectiveAlpha = this->m_alpha * this->alphaBD / 255;
+
+    for (auto child = this->m_children.Head(); child; child = this->m_children.Link(child)->Next()) {
+        child->frame->alphaBD = effectiveAlpha;
+        child->frame->UpdateAlpha();
+    }
+}
diff --git a/src/ui/CSimpleFrame.hpp b/src/ui/CSimpleFrame.hpp
index ce3e45f..4222ed1 100644
--- a/src/ui/CSimpleFrame.hpp
+++ b/src/ui/CSimpleFrame.hpp
@@ -35,6 +35,8 @@ class CSimpleFrame : public CScriptRegion {
         int32_t m_id = 0;
         uint32_t m_flags = 0;
         float m_frameScale = 1.0f;
+        uint8_t m_alpha = 255;
+        uint8_t alphaBD = 255;
         float m_depth = 0.0;
         FRAME_STRATA m_strata = FRAME_STRATA_MEDIUM;
         int32_t m_level = 0;
@@ -112,6 +114,7 @@ class CSimpleFrame : public CScriptRegion {
         virtual int32_t HideThis();
         virtual int32_t ShowThis();
         virtual bool UpdateScale(bool a2);
+        virtual void UpdateAlpha();
         virtual void UpdateDepth(bool a2);
         virtual void ParentFrame(CSimpleFrame* frame);
         virtual void OnFrameSizeChanged(const CRect& rect);