diff --git a/aniphallow.lua b/aniphallow.lua
index c421c0a..5224899 100644
--- a/aniphallow.lua
+++ b/aniphallow.lua
@@ -2660,26 +2660,30 @@ openMainDialog = function()
         text = "Analyze",
         visible = false,
         onclick = function()
-            app.alert("ANALYZE CLICKED - build 1919ad8+1")
             -- Always refresh to avoid stale image from a different sprite
             refreshSource()
             if not S.sourceImage then
                 app.alert("No source image. Open a sprite first.")
                 return
             end
-            -- Diagnostics
-            local diag = "mode=" .. S.gbAnalyzeMode ..
-                " tileW=" .. S.gbTileW .. " tileH=" .. S.gbTileH ..
-                " imgW=" .. tostring(S.sourceImage.width) ..
-                " imgH=" .. tostring(S.sourceImage.height)
             if S.sourceImage.width == 0 or S.sourceImage.height == 0 then
-                app.alert("Source image has zero size. " .. diag)
+                app.alert("Source image has zero size")
                 return
             end
             if S.gbTileW < 1 or S.gbTileH < 1 then
-                app.alert("Bad tile size. " .. diag)
+                app.alert("Bad tile size: " .. S.gbTileW .. "x" .. S.gbTileH)
                 return
             end
+            -- Count non-transparent pixels in source
+            local nonEmptyPixels = 0
+            local sampleW = math.min(S.sourceImage.width, 200)
+            local sampleH = math.min(S.sourceImage.height, 200)
+            for y = 0, sampleH - 1 do
+                for x = 0, sampleW - 1 do
+                    local px = S.sourceImage:getPixel(x, y)
+                    if pc.rgbaA(px) > 0 then nonEmptyPixels = nonEmptyPixels + 1 end
+                end
+            end
             local usedTileW = S.gbTileW
             local usedTileH = S.gbTileH
             if S.gbAnalyzeMode == "tile" then
@@ -2690,6 +2694,14 @@ openMainDialog = function()
             else
                 S.gbTiles, S.gbTotalTiles = analyzeTiles(S.sourceImage, S.gbFlipOpt, S.gbOffsetOpt, usedTileW, usedTileH)
             end
+            if S.gbTotalTiles == 0 then
+                app.alert("0/0 result. mode=" .. S.gbAnalyzeMode ..
+                    " tile=" .. usedTileW .. "x" .. usedTileH ..
+                    " img=" .. S.sourceImage.width .. "x" .. S.sourceImage.height ..
+                    " nonEmptyPx(200x200)=" .. nonEmptyPixels ..
+                    " cm=" .. tostring(S.sourceImage.colorMode) ..
+                    " spriteCM=" .. tostring(app.sprite and app.sprite.colorMode or "nil"))
+            end
             S.gbTileW = usedTileW
             S.gbTileH = usedTileH
             S.gbOptImage, S.gbCols = buildOptimizedImage(