With that code, I added it here: https://jsfiddle.net/0rwv6h95/4/
It didn’t do anything.
I was supposed to be able to see through the container.
.container {
position: relative;
max-width: 642px;
margin: 15px auto 30px;
padding: 15px;
/*box-shadow: 0 0 0 rgb(0 0 0 / 20%);*/
border: 1px solid #0059dd;
border-radius: 0;
background: linear-gradient(45deg,
transparent,
transparent 7px,
rgb(113, 121, 126) 7px,
rgb(113, 121, 126) 7.5px,
transparent 7.5px,
transparent 10px),
linear-gradient(-45deg,
transparent,
transparent 7px,
rgb(113, 121, 126) 7px,
rgb(113, 121, 126) 7.5px,
transparent 7.5px,
transparent 10px);
background-size: 10px 10px;
}
.container::before {
content: "";
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
margin: auto;
width: 94.96%;
height: 90.91%;
background: transparent;
-webkit-mask-image:
linear-gradient(to top, transparent, #fff) top /100% 20%,
linear-gradient(to bottom, transparent, #fff) bottom/100% 20%,
linear-gradient(to left, transparent, #fff) left /20% 100%,
linear-gradient(to right, transparent, #fff) right /20% 100%;
mask-image:
linear-gradient(to top, transparent, #fff) top /100% 20%,
linear-gradient(to bottom, transparent, #fff) bottom/100% 20%,
linear-gradient(to left, transparent, #fff) left /20% 100%,
linear-gradient(to right, transparent, #fff) right /20% 100%;
mask-repeat: no-repeat;
}