I’m new in writing Unity Shaders.
I create a capsule and give it a simple texture, using a pixel-level Blinn-Phong lightning model to write a shader. But the result seems wrong:

1. Specular term seems too big
   if I change the “_Specular” property to “white”, you can see the result
2. the line between dark and light is too sharp
3. no matter how I change the Light position (Unity default setting, Directional light), the color of the capsule doesn’t change
   Here’s my shader code:

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Single Texture" {
    Properties {
        _Color ("Color Tint", Color) = (1, 1, 1, 1)
        _MainTex ("Main Tex", 2D) = "white" {}
        _Specular ("Specular", Color) = (1, 1, 1, 1)
        _Gloww ("Gloss", Range(8.0, 256)) = 20
    }
    SubShader {
         Pass {
             Tags { "LightMode"="ForwardBase"}

             CGPROGRAM

             #pragma vertex vert
             #pragma fragment frag

             #include <Lighting.cginc>

             fixed4 _Color;
             sampler2D _MainTex;
             float4 _MainTex_ST;
             fixed4 _Specular;
             float _Gloss;

             struct a2v {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                float4 texcoord : TEXCOORD0;
              };

              struct v2f {
                  float4 pos : SV_POSITION;
                  float3 worldNormal : TEXCOORD0;
                  float3 worldPos : TEXCOORD1;
                  float2 uv : TEXCOORD2;
              };


              v2f vert(a2v v) {
                  v2f o;
                  o.pos = UnityObjectToClipPos(v.vertex);
                  o.worldNormal = UnityObjectToWorldNormal(v.normal);
                  o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                  o.uv = v.texcoord.xy * _MainTex_ST.xy + _MainTex_ST.zw;
                  return o;
              }

              fixed4 frag(v2f i) : SV_TARGET {
                  fixed3 worldNormal = normalize(i.worldNormal);
                  fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));

                  fixed3 albedo = tex2D(_MainTex, i.uv).rgb * _Color.rgb;

                  fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;

                  fixed3 diffuse = _LightColor0.rgb * albedo * saturate(dot(worldNormal, worldLightDir));

                  fixed3 viewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));
                  fixed3 halfDir = normalize(worldLightDir + viewDir);
                  fixed3 specular = _LightColor0.rgb * _Specular.rgb * pow(max(0, dot(worldNormal, halfDir)), _Gloss);

                  return fixed4(ambient + diffuse + specular, 1.0);
              }

             ENDCG
         }
    }
    Fallback "Specular"
}

Here’s my wrong capsule:
enter image description here

Actually I’m following a Unity Shader Tutorial Book, I check the code in the book and it turns out that mine seems identical to it.
I wonder the problem is about some kind of setting or..
Hope someone could show me the problem, I’d really appreciate -w-