From 36a4677c21646adff0bcfc9a71a49d3a025220a2 Mon Sep 17 00:00:00 2001
From: hexagonhexagon <hexagonhexagon163@gmail.com>
Date: Tue, 30 Jun 2020 17:46:48 -0400
Subject: [PATCH] Ensure that layerToMergeAt is not less than 0.

---
 src/js/game/shape_definition.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/js/game/shape_definition.js b/src/js/game/shape_definition.js
index 0896d473..44fbbb3c 100644
--- a/src/js/game/shape_definition.js
+++ b/src/js/game/shape_definition.js
@@ -536,7 +536,8 @@ export class ShapeDefinition extends BasicSerializableObject {
             gapsBetweenShapes.push(topShapeLowestLayerByQuad[quad] - bottomShapeHighestLayerByQuad[quad]);
         }
         const smallestGapBetweenShapes = Math.min(...gapsBetweenShapes);
-        const layerToMergeAt = 1 - smallestGapBetweenShapes;
+        // Can't merge at a layer lower than 0
+        const layerToMergeAt = Math.max(1 - smallestGapBetweenShapes, 0);
 
         const mergedLayers = this.internalCloneLayers();
         for (let layer = mergedLayers.length; layer < layerToMergeAt + topShapeLayers.length; ++layer) {