diff --git a/assets/index.html b/assets/index.html
index 3300045..cd3a253 100644
--- a/assets/index.html
+++ b/assets/index.html
@@ -117,7 +117,11 @@
         var top3 = project(wx + TILE - GAP/2, wy + GAP/2, h * HEIGHT_UNIT);
         var top4 = project(wx + GAP/2, wy + GAP/2, h * HEIGHT_UNIT);
 
-        var topColor = '#5a8a5a';
+        var heightFactor = Math.min(1, Math.max(0, h / 15));
+        var topR = Math.floor(90 - heightFactor * 30);
+        var topG = Math.floor(138 - heightFactor * 30);
+        var topB = Math.floor(90 - heightFactor * 30);
+        var topColor = 'rgb(' + topR + ',' + topG + ',' + topB + ')';
         var rightColor = '#6b4423';
         var leftColor = '#3d2614';