Remove a leftover use of var in Chapter 16

Author: marijnh

16_game.md

@@ -847,13 +847,13 @@ and a size) touches a grid element of the given type.
 
 ```{includeCode: true}
 Level.prototype.touches = function(pos, size, type) {
-  var xStart = Math.floor(pos.x);
-  var xEnd = Math.ceil(pos.x + size.x);
-  var yStart = Math.floor(pos.y);
-  var yEnd = Math.ceil(pos.y + size.y);
+  let xStart = Math.floor(pos.x);
+  let xEnd = Math.ceil(pos.x + size.x);
+  let yStart = Math.floor(pos.y);
+  let yEnd = Math.ceil(pos.y + size.y);
 
-  for (var y = yStart; y < yEnd; y++) {
-    for (var x = xStart; x < xEnd; x++) {
+  for (let y = yStart; y < yEnd; y++) {
+    for (let x = xStart; x < xEnd; x++) {
       let isOutside = x < 0 || x >= this.width ||
                       y < 0 || y >= this.height;
       let here = isOutside ? "wall" : this.rows[y][x];

html/errata.html

@@ -93,6 +93,11 @@ <h2>Chapter 15</h2>
 
 <h2>Chapter 16</h2>
 
+<p><strong>Page 278</strong> <em>Motion and Collision</em>: The code
+that defines the <code>touches</code> method unintentionally (though
+harmlessly) used <code>var</code> instead of <code>let</code> to
+define variables.</p>
+
 <p><strong>Page 285</strong> (2nd) <em>Pausing the Game</em>: The text
 refers to the <code>arrow</code> binding, where it should
 say <code>arrowKeys</code>.</p>