diff --git a/lib/window.rb b/lib/window.rb
index 8bdca77..03bb77e 100644
--- a/lib/window.rb
+++ b/lib/window.rb
@@ -186,8 +186,10 @@ class IMICFPS
         $debug = !$debug
       when Gosu::MsWheelUp
         @initial_fov += 1
+        @initial_fov = @initial_fov.clamp(1, 179)
       when Gosu::MsWheelDown
         @initial_fov -= 1
+        @initial_fov = @initial_fov.clamp(1, 179)
       end
     end
 
diff --git a/objects/plane.mtl b/objects/plane.mtl
new file mode 100644
index 0000000..65e529d
--- /dev/null
+++ b/objects/plane.mtl
@@ -0,0 +1,11 @@
+# Blender MTL File: 'None'
+# Material Count: 1
+
+newmtl None
+Ns 0
+Ka 0.000000 0.000000 0.000000
+Kd 0.8 0.8 0.8
+Ks 0.8 0.8 0.8
+d 1
+illum 2
+map_Kd objects/skydome.png
diff --git a/objects/plane.obj b/objects/plane.obj
new file mode 100644
index 0000000..3c5f0df
--- /dev/null
+++ b/objects/plane.obj
@@ -0,0 +1,17 @@
+# Blender v2.79 (sub 0) OBJ File: ''
+# www.blender.org
+mtllib plane.mtl
+o Plane
+v -999.999939 0.000000 999.999939
+v 999.999939 0.000000 999.999939
+v -999.999939 0.000000 -999.999939
+v 999.999939 0.000000 -999.999939
+vt 0.395761 0.622989
+vt 0.116739 0.902011
+vt 0.116739 0.622989
+vt 0.395761 0.902011
+vn 0.0000 1.0000 0.0000
+usemtl None
+s off
+f 2/1/1 3/2/1 1/3/1
+f 2/1/1 4/4/1 3/2/1