Trying to blend 2 textures along a gradient in CG

OK so I'm trying my hand at writing a shader in CG. It's supposed to use two textures that blend together along inverse gradients.

The first version here is with only the first texture worked in:

Code (csharp):

1. Shader "Tutorial/Textured Colored v1" {
2. Properties {
3.     _MainTex ("Texture", 2D) = "white" { }
4.     _BlendText ("Texture", 2D) = "black" { }
5. }
6. SubShader {
7.     Pass {
8.  
9. CGPROGRAM
10. #pragma vertex vert
11. #pragma fragment frag
12. #pragma fragmentoption ARB_fog_exp2
13.  
14. #include "UnityCG.cginc"
15.  
16. sampler2D _MainTex;
17. sampler2D _BlendTex;
18.  
19. struct v2f {
20.     V2F_POS_FOG;
21.     float2  uv : TEXCOORD0;
22. };
23.  
24. v2f vert (appdata_base v)
25. {
26.     v2f o;
27.     PositionFog( v.vertex, o.pos, o.fog );
28.     o.uv = TRANSFORM_UV(0);
29.     return o;
30. }
31.  
32. half4 frag (v2f i) : COLOR
33. {
34.     float alpha = i.uv;
35.     half4 texcol = tex2D( _MainTex, i.uv );
36.     return texcol * (1,1,1,alpha);
37. }
38. ENDCG
39.  
40.     }
41. }
42. Fallback "VertexLit"
43. }

It seems to work pretty well: http://www.ohlonegdc.com/file-host/shader_v1.jpg

Ok, but when I try to include the second texture along the inverse gradient, here is the code:

Code (csharp):

1. Shader "Tutorial/Textured Colored" {
2. Properties {
3.     _MainTex ("Texture", 2D) = "white" { }
4.     _BlendText ("Texture", 2D) = "black" { }
5. }
6. SubShader {
7.     Pass {
8.  
9. CGPROGRAM
10. #pragma vertex vert
11. #pragma fragment frag
12. #pragma fragmentoption ARB_fog_exp2
13.  
14. #include "UnityCG.cginc"
15.  
16. sampler2D _MainTex;
17. sampler2D _BlendTex;
18.  
19. struct v2f {
20.     V2F_POS_FOG;
21.     float2  uv : TEXCOORD0;
22.     float2 uv2 : TEXCOORD1;
23. };
24.  
25. v2f vert (appdata_base v)
26. {
27.     v2f o;
28.     PositionFog( v.vertex, o.pos, o.fog );
29.     o.uv = TRANSFORM_UV(0);
30.     o.uv2 = TRANSFORM_UV(1);
31.     return o;
32. }
33.  
34. half4 frag (v2f i) : COLOR
35. {
36.     float alpha = i.uv;
37.     float inverseAlpha = 1 - i.uv2;
38.     half4 texcol = tex2D( _MainTex, i.uv ) * (1,1,1,alpha);
39.     half4 texcolblend = tex2D( _BlendTex, i.uv2) * (1,1,1,inverseAlpha);
40.     return texcol + texcolblend;
41. }
42. ENDCG
43.  
44.     }
45. }
46. Fallback "VertexLit"
47. }

And the result looks like the second texture is just being interpreted as a solid color: http://www.ohlonegdc.com/file-host/shader_v2.jpg

Any idea what's happening here? I appreciate any help in advance.

 

Turns out I had a typo!

Anyone know a way to rotate a texture along existing UVs? That would be a time-saver.