diff --git a/BoxImage.class.php b/BoxImage.class.php
index f83b6ee..c0f8778 100644
--- a/BoxImage.class.php
+++ b/BoxImage.class.php
@@ -111,11 +111,11 @@ class BoxImage {
 				//if we go back
 			if($step === -1) {
 					//decrease x-pointer
-				$this->pointer_x--;
+				$this->pointer_x -= 1;
 					//handle y-jumps
-				if($this->pointer_x === 0) {
+				if($this->pointer_x < 0) {
 					$this->pointer_x = $width;
-					$this->pointer_y--;
+					$this->pointer_y -= 1;
 						//out of range?
 					if($this->pointer_y < 0) throw new Exception("Out of range! (width)");
 				}
@@ -123,11 +123,11 @@ class BoxImage {
 				//if we go forward
 			} elseif($step === 1) {
 			 		//increase x-pointer
-				$this->pointer_x++;
+				$this->pointer_x += 1;
 					//handle y-jumps
-				if($this->pointer_x === $this->width) {
+				if($this->pointer_x > $this->width) {
 					$this->pointer_x = 0;
-					$this->pointer_y++;
+					$this->pointer_y += 1;
 						//out of range?
 					if($this->pointer_y > $this->height) throw new Exception("Out of range! (height)");
 				}
diff --git a/test.jpg b/test.jpg
new file mode 100644
index 0000000..6ee6d4b
Binary files /dev/null and b/test.jpg differ