Remove this line
Code:
cnd r0.a,r0.a,c0,c1 // if(r0.a>0.5){r0.a=1;}else{r0.a=0;}

then uncomment the last line
or change the last line into:
Code:
mul r0,r0,x // modulate with lighting

Where X is anything from 0 to 1.

Ohh, it's remind me of the Low Level Language asm-shader days tongue