diff --git a/LEGO1/lego/legoomni/src/common/mxtransitionmanager.cpp b/LEGO1/lego/legoomni/src/common/mxtransitionmanager.cpp
index 27086eb3..b66b26e4 100644
--- a/LEGO1/lego/legoomni/src/common/mxtransitionmanager.cpp
+++ b/LEGO1/lego/legoomni/src/common/mxtransitionmanager.cpp
@@ -271,8 +271,15 @@ void MxTransitionManager::DissolveTransition()
 // FUNCTION: LEGO1 0x1004bed0
 void MxTransitionManager::MosaicTransition()
 {
+	static LPDIRECTDRAWSURFACE g_transitionSurface = nullptr;
+	static MxU32 g_colors[64][48];
+
 	if (m_animationTimer == 16) {
 		m_animationTimer = 0;
+		if (g_transitionSurface) {
+			g_transitionSurface->Release();
+			g_transitionSurface = nullptr;
+		}
 		EndTransition(TRUE);
 		return;
 	}
@@ -297,6 +304,84 @@ void MxTransitionManager::MosaicTransition()
 			for (i = 0; i < 48; i++) {
 				m_randomShift[i] = SDL_rand(64);
 			}
+
+			DDSURFACEDESC srcDesc = {};
+			srcDesc.dwSize = sizeof(srcDesc);
+			HRESULT lockRes = m_ddSurface->Lock(NULL, &srcDesc, DDLOCK_WAIT | DDLOCK_READONLY, NULL);
+			if (lockRes == DDERR_SURFACELOST) {
+				m_ddSurface->Restore();
+				lockRes = m_ddSurface->Lock(NULL, &srcDesc, DDLOCK_WAIT | DDLOCK_READONLY, NULL);
+			}
+
+			if (lockRes != DD_OK) {
+				return;
+			}
+
+			MxS32 bytesPerPixel = srcDesc.ddpfPixelFormat.dwRGBBitCount / 8;
+
+			for (MxS32 col = 0; col < 64; col++) {
+				for (MxS32 row = 0; row < 48; row++) {
+					MxS32 xBlock = (m_randomShift[row] + col) % 64;
+					MxS32 y = row * 10;
+					MxS32 x = xBlock * 10;
+
+					MxU8* pixelPtr = (MxU8*) srcDesc.lpSurface + y * srcDesc.lPitch + x * bytesPerPixel;
+
+					MxU32 pixel;
+					switch (bytesPerPixel) {
+					case 1:
+						pixel = *pixelPtr;
+						break;
+					case 2:
+						pixel = *(MxU16*) pixelPtr;
+						break;
+					default:
+						pixel = *(MxU32*) pixelPtr;
+						break;
+					}
+
+					g_colors[col][row] = pixel;
+				}
+			}
+
+			m_ddSurface->Unlock(srcDesc.lpSurface);
+
+			DDSURFACEDESC mainDesc = {};
+			mainDesc.dwSize = sizeof(mainDesc);
+			if (m_ddSurface->GetSurfaceDesc(&mainDesc) != DD_OK) {
+				return;
+			}
+
+			DDSURFACEDESC tempDesc = {};
+			tempDesc.dwSize = sizeof(tempDesc);
+			tempDesc.dwFlags = DDSD_WIDTH | DDSD_HEIGHT | DDSD_PIXELFORMAT | DDSD_CAPS;
+			tempDesc.dwWidth = 64;
+			tempDesc.dwHeight = 48;
+			tempDesc.ddpfPixelFormat = mainDesc.ddpfPixelFormat;
+			tempDesc.ddsCaps.dwCaps = DDSCAPS_OFFSCREENPLAIN;
+
+			if (MVideoManager()->GetDirectDraw()->CreateSurface(&tempDesc, &g_transitionSurface, nullptr) != DD_OK) {
+				return;
+			}
+
+			DWORD fillColor = 0x00000000;
+			switch (mainDesc.ddpfPixelFormat.dwRGBBitCount) {
+			case 8:
+				fillColor = 0x10;
+				break;
+			case 16:
+				fillColor = RGB555_CREATE(0x1f, 0, 0x1f);
+				break;
+			}
+
+			DDBLTFX bltFx = {};
+			bltFx.dwSize = sizeof(bltFx);
+			bltFx.dwFillColor = fillColor;
+			g_transitionSurface->Blt(NULL, NULL, NULL, DDBLT_COLORFILL | DDBLT_WAIT, &bltFx);
+
+			DDCOLORKEY key = {};
+			key.dwColorSpaceLowValue = key.dwColorSpaceHighValue = fillColor;
+			g_transitionSurface->SetColorKey(DDCKEY_SRCBLT, &key);
 		}
 
 		// Run one tick of the animation
@@ -304,15 +389,18 @@ void MxTransitionManager::MosaicTransition()
 		memset(&ddsd, 0, sizeof(ddsd));
 		ddsd.dwSize = sizeof(ddsd);
 
-		HRESULT res = m_ddSurface->Lock(NULL, &ddsd, DDLOCK_WAIT, NULL);
+		HRESULT res = g_transitionSurface->Lock(NULL, &ddsd, DDLOCK_WAIT | DDLOCK_WRITEONLY, NULL);
 		if (res == DDERR_SURFACELOST) {
-			m_ddSurface->Restore();
-			res = m_ddSurface->Lock(NULL, &ddsd, DDLOCK_WAIT, NULL);
+			g_transitionSurface->Restore();
+			res = g_transitionSurface->Lock(NULL, &ddsd, DDLOCK_WAIT | DDLOCK_WRITEONLY, NULL);
 		}
 
 		if (res == DD_OK) {
 			SubmitCopyRect(&ddsd);
 
+			// Combine xShift with this value to target the correct location in the buffer.
+			MxS32 bytesPerPixel = ddsd.ddpfPixelFormat.dwRGBBitCount / 8;
+
 			for (MxS32 col = 0; col < 64; col++) {
 				// Select 4 columns on each tick
 				if (m_animationTimer * 4 > m_columnOrder[col]) {
@@ -324,69 +412,29 @@ void MxTransitionManager::MosaicTransition()
 				}
 
 				for (MxS32 row = 0; row < 48; row++) {
-					// To do the mosaic effect, we subdivide the 640x480 surface into
-					// 10x10 pixel blocks. At the chosen block, we sample the top-leftmost
-					// color and set the other 99 pixels to that value.
+					MxS32 x = (m_randomShift[row] + col) % 64;
+					MxU8* dest = (MxU8*) ddsd.lpSurface + row * ddsd.lPitch + x * bytesPerPixel;
 
-					// First, get the offset of the 10x10 block that we will sample for this row.
-					MxS32 xShift = 10 * ((m_randomShift[row] + col) % 64);
-
-					// Combine xShift with this value to target the correct location in the buffer.
-					MxS32 bytesPerPixel = ddsd.ddpfPixelFormat.dwRGBBitCount / 8;
-
-					// Seek to the sample position.
-					MxU8* source = (MxU8*) ddsd.lpSurface + 10 * row * ddsd.lPitch + bytesPerPixel * xShift;
-
-					// Sample byte or word depending on display mode.
-					MxU32 sample;
+					MxU32 source = g_colors[col][row];
 					switch (bytesPerPixel) {
 					case 1:
-						sample = *source;
+						*dest = (MxU8) source;
 						break;
 					case 2:
-						sample = *(MxU16*) source;
+						*((MxU16*) dest) = (MxU16) source;
 						break;
 					default:
-						sample = *(MxU32*) source;
+						*((MxU32*) dest) = source;
 						break;
 					}
-
-					// For each of the 10 rows in the 10x10 square:
-					for (MxS32 k = 10 * row; k < 10 * row + 10; k++) {
-						void* pos = (MxU8*) ddsd.lpSurface + k * ddsd.lPitch + bytesPerPixel * xShift;
-
-						switch (bytesPerPixel) {
-						case 1: {
-							// Optimization: If the pixel is only one byte, we can use memset
-							memset(pos, sample, 10);
-							break;
-						}
-						case 2: {
-							MxU16* p = (MxU16*) pos;
-							for (MxS32 tt = 0; tt < 10; tt++) {
-								p[tt] = (MxU16) sample;
-							}
-							break;
-						}
-						default: {
-							MxU32* p = (MxU32*) pos;
-							for (MxS32 tt = 0; tt < 10; tt++) {
-								p[tt] = (MxU32) sample;
-							}
-							break;
-						}
-						}
-					}
 				}
 			}
 
 			SetupCopyRect(&ddsd);
-			m_ddSurface->Unlock(ddsd.lpSurface);
+			g_transitionSurface->Unlock(ddsd.lpSurface);
 
-			if (VideoManager()->GetVideoParam().Flags().GetFlipSurfaces()) {
-				LPDIRECTDRAWSURFACE surf = VideoManager()->GetDisplaySurface()->GetDirectDrawSurface1();
-				surf->BltFast(0, 0, m_ddSurface, &g_fullScreenRect, DDBLTFAST_WAIT);
-			}
+			RECT srcRect = {0, 0, 64, 48};
+			m_ddSurface->Blt(&g_fullScreenRect, g_transitionSurface, &srcRect, DDBLT_WAIT | DDBLT_KEYSRC, NULL);
 
 			m_animationTimer++;
 		}
diff --git a/miniwin/include/miniwin/ddraw.h b/miniwin/include/miniwin/ddraw.h
index 2a8932a2..0250c099 100644
--- a/miniwin/include/miniwin/ddraw.h
+++ b/miniwin/include/miniwin/ddraw.h
@@ -162,9 +162,11 @@ ENABLE_BITMASK_OPERATORS(DDBltFastFlags)
 #define DDLOCK_SURFACEMEMORYPTR DDLockFlags::SURFACEMEMORYPTR
 #define DDLOCK_WAIT DDLockFlags::WAIT
 #define DDLOCK_WRITEONLY DDLockFlags::WRITEONLY
+#define DDLOCK_READONLY DDLockFlags::READONLY
 enum class DDLockFlags : uint32_t {
 	SURFACEMEMORYPTR = 0,
 	WAIT = 1 << 0,
+	READONLY = 1 << 4,
 	WRITEONLY = 1 << 5,
 };
 ENABLE_BITMASK_OPERATORS(DDLockFlags)
diff --git a/miniwin/src/ddraw/ddsurface.cpp b/miniwin/src/ddraw/ddsurface.cpp
index de250dea..056912fd 100644
--- a/miniwin/src/ddraw/ddsurface.cpp
+++ b/miniwin/src/ddraw/ddsurface.cpp
@@ -52,6 +52,24 @@ HRESULT DirectDrawSurfaceImpl::Blt(
 	LPDDBLTFX lpDDBltFx
 )
 {
+	if ((dwFlags & DDBLT_COLORFILL) == DDBLT_COLORFILL) {
+		Uint8 a = (lpDDBltFx->dwFillColor >> 24) & 0xFF;
+		Uint8 r = (lpDDBltFx->dwFillColor >> 16) & 0xFF;
+		Uint8 g = (lpDDBltFx->dwFillColor >> 8) & 0xFF;
+		Uint8 b = lpDDBltFx->dwFillColor & 0xFF;
+
+		const SDL_PixelFormatDetails* details = SDL_GetPixelFormatDetails(m_surface->format);
+		Uint32 color = SDL_MapRGBA(details, nullptr, r, g, b, a);
+		if (lpDestRect) {
+			SDL_Rect dstRect = ConvertRect(lpDestRect);
+			SDL_FillSurfaceRect(m_surface, &dstRect, color);
+		}
+		else {
+			SDL_FillSurfaceRect(m_surface, nullptr, color);
+		}
+		return DD_OK;
+	}
+
 	auto other = static_cast<DirectDrawSurfaceImpl*>(lpDDSrcSurface);
 
 	SDL_Rect srcRect = lpSrcRect ? ConvertRect(lpSrcRect) : SDL_Rect{0, 0, other->m_surface->w, other->m_surface->h};
diff --git a/miniwin/src/ddraw/framebuffer.cpp b/miniwin/src/ddraw/framebuffer.cpp
index ea66e96b..13caa434 100644
--- a/miniwin/src/ddraw/framebuffer.cpp
+++ b/miniwin/src/ddraw/framebuffer.cpp
@@ -171,6 +171,9 @@ HRESULT FrameBufferImpl::Lock(LPRECT lpDestRect, DDSURFACEDESC* lpDDSurfaceDesc,
 	if (!DDRenderer) {
 		return DDERR_GENERIC;
 	}
+
+	m_readOnlyLock = (dwFlags & DDLOCK_READONLY) == DDLOCK_READONLY;
+
 	if ((dwFlags & DDLOCK_WRITEONLY) == DDLOCK_WRITEONLY) {
 		const SDL_PixelFormatDetails* details = SDL_GetPixelFormatDetails(m_transferBuffer->m_surface->format);
 		SDL_Palette* palette = m_palette ? static_cast<DirectDrawPaletteImpl*>(m_palette)->m_palette : nullptr;
@@ -223,7 +226,9 @@ HRESULT FrameBufferImpl::SetPalette(LPDIRECTDRAWPALETTE lpDDPalette)
 HRESULT FrameBufferImpl::Unlock(LPVOID lpSurfaceData)
 {
 	m_transferBuffer->Unlock(lpSurfaceData);
-	BltFast(0, 0, m_transferBuffer, nullptr, DDBLTFAST_WAIT);
+	if (!m_readOnlyLock) {
+		BltFast(0, 0, m_transferBuffer, nullptr, DDBLTFAST_WAIT);
+	}
 
 	return DD_OK;
 }
diff --git a/miniwin/src/internal/framebuffer_impl.h b/miniwin/src/internal/framebuffer_impl.h
index 5e40f7e8..47805e69 100644
--- a/miniwin/src/internal/framebuffer_impl.h
+++ b/miniwin/src/internal/framebuffer_impl.h
@@ -39,6 +39,7 @@ struct FrameBufferImpl : public IDirectDrawSurface3 {
 private:
 	uint32_t m_virtualWidth;
 	uint32_t m_virtualHeight;
+	bool m_readOnlyLock;
 	DirectDrawSurfaceImpl* m_transferBuffer;
 	IDirectDrawPalette* m_palette = nullptr;
 };