diff --git a/src/image.rs b/src/image.rs
index 6011551..d456b81 100644
--- a/src/image.rs
+++ b/src/image.rs
@@ -57,7 +57,7 @@ impl Image {
     }
 
     pub fn get_pixel(&mut self, x: i32, y: i32) -> Option<&mut Pixel> {
-        if x >= self.width || y >= self.height {
+        if x >= self.width || y >= self.height || x < 0 || y < 0{
             return None;
         }
 
diff --git a/src/object.rs b/src/object.rs
index 68e0ea5..26cfeb4 100644
--- a/src/object.rs
+++ b/src/object.rs
@@ -60,9 +60,9 @@ impl Hittable for Sphere {
 
         let sqrtd = discriminant.sqrt();
         let mut root = (h - sqrtd) / a;
-        if !interval.surounds(root) {
+        if !interval.surrounds(root) {
             root = (h + sqrtd) / a;
-            if !interval.surounds(root)  {
+            if !interval.surrounds(root)  {
                 return None;
             }
         }
diff --git a/src/vec3.rs b/src/vec3.rs
index 95a4077..0b4eaeb 100644
--- a/src/vec3.rs
+++ b/src/vec3.rs
@@ -41,7 +41,7 @@ impl Interval {
 	self.min <= x && x <= self.max
     }
 
-    pub fn surounds(self, x:f64) -> bool {
+    pub fn surrounds(self, x:f64) -> bool {
 	self.min < x && x < self.max
     }
 }
@@ -136,21 +136,21 @@ impl Vec3 {
         self.x * other.x + self.y * other.y + self.z * other.z
     }
 
-    pub fn x(self) -> f64 {
+    pub fn x(&self) -> f64 {
         self.x
     }
 
-    pub fn y(self) -> f64 {
+    pub fn y(&self) -> f64 {
         self.y
     }
 
-    pub fn z(self) -> f64 {
+    pub fn z(&self) -> f64 {
         self.z
     }
 
     pub fn cross(self, other: Vec3) -> Vec3 {
         let x = self.y * other.z - self.z * other.y;
-        let y = self.y * other.x - self.x * other.y;
+        let y = self.z * other.x - self.x * other.z;
         let z = self.x * other.y - self.y * other.x;
         Vec3 { x, y, z }
     }
@@ -164,6 +164,10 @@ impl Vec3 {
     }
 
     pub fn unit(self) -> Vec3 {
-        self / self.length()
+	if self.length() == 0.0{
+	    self
+	} else {
+            self / self.length()
+	}
     }
 }