Error when opening traceGL interface #118

Uncaught Error: Could not link, max varying:15
precision mediump float;
#define ucol vec4
uniform vec4 ps;
uniform vec4 sz;
uniform float fg;
uniform sampler2D T;
vec2 f;
uniform vec2 s;
uniform ucol N_g;
varying vec4 rv_;
vec4 r;
vec4 _f(){
vec3 v = vec3(floor(ps.z+(ps.x+r.x)*sz.x),floor(ps.w+(ps.y+r.y)*sz.y-sz.z),ps.z+(ps.x+r.z)*sz.x);
vec4 c = vec4((texture2D(T,vec2((fg),0.))));
;
if(f.x<v.x+0.5*sz.x){
vec2 d = vec2(f.x-(v.x+sz.x),f.y-(v.y+0.5*sz.y));
;
if(d.y<0.&&mod(r.w,2.)==1.)return vec4(c);
;
if(d.y>0.&&mod(r.w,4.)>=2.)return vec4(c);
return vec4(c.xyz,sqrt(d.x*d.x+d.y*d.y)>9.?0.:c.w);
;
}
else ;
if(f.x>v.z-0.5*sz.x){
vec2 d = vec2(f.x-(v.z-sz.x),f.y-(v.y+0.5*sz.y));
;
if(d.y<0.&&mod(r.w,8.)>=4.)return vec4(c);
;
if(d.y>0.&&mod(r.w,16.)>=8.)return vec4(c);
return vec4(c.xyz,sqrt(d.x*d.x+d.y*d.y)>9.?0.:c.w);
;
}
return vec4(c);
;
}
void main(void){
 r = rv_;
f = vec2(gl_FragCoord.x,s.y-gl_FragCoord.y);
 gl_FragColor = _f();
}.