diff --git a/herzle.html b/herzle.html
index 1db94b8..eb16fa9 100644
--- a/herzle.html
+++ b/herzle.html
@@ -8,6 +8,7 @@
       font-size: 50px;
       color: #ff00ff;
       font-family: helvetica, arial;
+      overflow: hidden;
     }
     #player {
       position: absolute;
diff --git a/herzle.js b/herzle.js
index 9511068..20c6307 100644
--- a/herzle.js
+++ b/herzle.js
@@ -13,10 +13,14 @@ function onKeyDown(e) {
   e = e || window.event;
 
   if (e.keyCode == '37') { // left
-    player_pos[0] -= 10;
+    if (player_pos[0] - 10 >= 0) {
+      player_pos[0] -= 10;
+    }
   }
   if (e.keyCode == '39') { // right
-    player_pos[0] += 10;
+    if (player_pos[0] + 10 <= window.innerWidth) {
+      player_pos[0] += 10;
+    }
   }
   if (e.keyCode == '32') { // space = fire
     if ((new Date()).getTime() - lastshoot > 300) {