css - why the drop shadow hide when the element move -

i have dive drop shadow using

    filter: drop-shadow(0 0 20px #fff);     -webkit-filter: drop-shadow(0 0 20px #fff); 

but drop shadow disappear when element moves. why , how prevent it. jsfiddle of code: https://jsfiddle.net/vu14anwv/ problem show in chrome, in fire fox every thing ok.

try drop-shadow on element want appear under.

.element-that-is-to-be-under{     filter: drop-shadow(0 0 20px #fff);     -webkit-filter: drop-shadow(0 0 20px #fff); }