.panel {
  position: relative;
  width: 300px;
  padding: 1em;
  background-color: #111216;
}

.panel .frame,
.panel .frame::before {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  box-sizing: border-box;
}

/* Gray border */
.frame.rim {
  border: 1px solid #303030;
  box-shadow:
    inset 0 0 0 1px #0a0a0a,
    0 0 0 1px #0a0a0a;
}

/* Green accent edges */
.frame.accent::before {
  content: '';
  background-image: linear-gradient(
    to top,
    #8bc34a,
    #33691e66 25%,
    transparent 70%
  );
  clip-path: polygon(
    /* Trace around the box clockwise */
    0 0,
    100% 0,
    100% 100%,
    0 100%,
    0 0,
    /* Move 1px inward and run back around counter-clockwise */
    1px 1px,
    1px calc(100% - 1px),
    calc(100% - 1px) calc(100% - 1px),
    calc(100% - 1px) 1px,
    1px 1px
  );
}

/* Glow is just a copy of the accent frame with a blur filter */
.frame.accent.glow {
  filter: blur(4px);
}

body {
  background-color: #0b0c0d;
  color: silver;
  font-family: Segoe UI,Helvetica Neue,Tahoma,Geneva,Verdana,sans-serif;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  margin: 0;
}