diff --git a/packages/topdown/tiles.js b/packages/topdown/tiles.js
index b76ab3a..304466e 100644
--- a/packages/topdown/tiles.js
+++ b/packages/topdown/tiles.js
@@ -60,6 +60,10 @@ export class Tiles extends decorate(class {}) {
     return this;
   }
 
+  indexAt(position) {
+    return this.width * position[1] + position[0];
+  }
+
   packetsForUpdate() {
     const packetsForUpdate = this.updatePackets;
     this.updatePackets = [];
@@ -117,7 +121,7 @@ export class Tiles extends decorate(class {}) {
   }
 
   tileAt(position) {
-    return this.data[position[1] * this.width + position[0]];
+    return this.data[this.indexAt(position)];
   }
 
   toJSON() {