diff --git a/vendor/clouds3d.js b/vendor/clouds3d.js
index bb76aec..d524183 100644
--- a/vendor/clouds3d.js
+++ b/vendor/clouds3d.js
@@ -334,7 +334,7 @@ function drawTileAt(lng, perp, dx, dz, centerTileX, centerTileY) {
     // For perp axis (X): keep the natural sign so world east (dx>0)
     // ends up at canvasX > halfPerp area (right side of canvas).
     var canvasX = (perp + halfPerp + 0.5) * GROUND_TILE_SIZE;
-    var canvasY = (-lng + halfLong + 0.5) * GROUND_TILE_SIZE;
+    var canvasY = (lng + halfLong + 0.5) * GROUND_TILE_SIZE;
     if (canvasX < 0 || canvasX >= groundCanvas.width || canvasY < 0 || canvasY >= groundCanvas.height) {
         return Promise.resolve(false);
     }