#iChannel0 "https://i.imgur.com/TnmUwCn.jpg"

vec4 BoxCoords(vec2 uv) {

    vec2 gv = fract(uv);
    vec2 id = floor(uv);
    //standard uv
    return vec4(gv.x, gv.y, id.x, id.y);
}

void mainImage ( out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = (fragCoord-0.5*iResolution.xy)/iResolution.y;
    
    vec3 col = vec3(0.0);
    uv.x *= 10.0;
    uv.y *= 5.0;
    
    vec4 coord = BoxCoords(uv);
    col.rgb = texture(iChannel0, coord.xy).rgb;
    col.rgb *= vec3(smoothstep(0.09, 0.99, sin(coord.z+coord.w/17.+iTime) ));

    fragColor = vec4(col, 1.0);
}